Add Calendar integration (read-only)

README.md

@@ -12,6 +12,7 @@ Minimal self-hosted personal wiki. Folders are pages.
 - **Wikilinks**: `[[query]]` or `[[query::label]]`. They open a search, so links still work after a page is renamed. Typing `[[` in the editor suggests page names. Embed files with `![caption](photo.jpg "left")`.
 - **Movie import**: create a page from OMDb metadata. Asks once for a free [OMDb API key](https://www.omdbapi.com/apikey.aspx) and keeps it in the browser.
 - **Special folders**: a [photo diary](#diary) and a [fitness dashboard](#fitness).
+- **Calendars**: Nextcloud calendars mirrored into the wiki. They add events and weight to the diary, and a [maintenance widget](#calendars) to every page.
 - **Quick-add bookmarklet**: save the current tab to a wiki page.
 - **Companion app**: an optional desktop helper, downloadable from the wiki footer. It opens wiki files in local apps and folders in the file manager.
 
@@ -33,6 +34,8 @@ GOOS=linux GOARCH=arm go build -o datascape .  # QNAP NAS
 | `-cache` | `./cache` | Thumbnail cache |
 | `-user`, `-pass` | | Basic auth (omit to disable) |
 | `-reindex-interval` | `30m` | Search index rebuild (`0` = off) |
+| `-calendars` | `Calendars` | [Calendars](#calendars) folder, relative to `-dir` (empty = off) |
+| `-tz` | system | Time zone for calendars and the diary, e.g. `Europe/Berlin` |
 
 ## `.page-settings`
 
@@ -43,7 +46,7 @@ Per-folder `key = value` file. The **view** button in the `Files` header sets th
 | `view` | `list`, `thumbnail` |
 | `sort` | `name`, `modified`, `size` |
 | `order` | `asc`, `desc` |
-| `type` | `diary`, `fitness` |
+| `type` | `diary`, `fitness`, `calendars` |
 
 ## Keyboard shortcuts
 
@@ -51,7 +54,7 @@ All use Alt+Shift.
 
 | Where | Keys |
 |-------|------|
-| Anywhere | `E` edit, `N` new page, `M` move, `F` search |
+| Anywhere | `E` edit, `N` new page, `M` move, `F` search, `H` maintenance |
 | Editor | `S` save, `1`–`3` heading, `B`/`I` bold/italic, `C`/`K` code/code block, `L` link, `P` wikilink, `G` embed, `U`/`O`/`X` bullet/numbered/task list, `Q` quote, `R` rule, `T` format table, `D`/`W` date (ISO/long), `V` movie, `Y` delete line |
 
 ## Diary
@@ -72,6 +75,46 @@ Bookmarkable shortcuts: `<diary>/today/`, `<diary>/this-month/`, `<diary>/this-y
 
 With `type = fitness`, a folder shows weight charts (daily and weekly mean, with your goal) below its content. Copy the [Waistline](https://github.com/davidhealey/waistline) app's export into the folder as `waistline_export.json`. Each new export replaces the old file.
 
+## Calendars
+
+```
+Calendars/
+  .page-settings   ← type = calendars, roles, sync credentials
+  Personal.ics     ← one file per calendar
+  Gewicht.ics
+  …
+```
+
+Pages only read these local files and never contact the calendar server. The built-in sync downloads all calendars of a CalDAV calendar home in the background. Or you can put the `.ics` files there yourself.
+
+```
+type = calendars
+
+# Roles: file names without .ics
+diary = Personal, Feiertage
+weight = Gewicht
+maintenance = Maintainance
+
+# Sync (Nextcloud)
+caldav-url = https://cloud.example/remote.php/dav/calendars/me/
+caldav-user = me
+caldav-pass = xxxxx-xxxxx-xxxxx-xxxxx-xxxxx
+sync-interval = 15m
+```
+
+| Key | |
+|-----|-|
+| `diary` | Events shown under each diary day: all-day first, then by start time |
+| `weight` | Titles like `95,6kg`, shown under the diary day's events |
+| `maintenance` | Tasks in the header widget (with the number due today) and on the calendars page |
+| `caldav-url` | Calendar home. Empty = no sync |
+| `caldav-user`, `caldav-pass` | Use a Nextcloud app password (Settings → Security), not the account password |
+| `sync-interval` | Default `15m`. `0` = only at startup and with **Sync now** |
+
+Changes apply without a restart. Each calendar is saved as `<display name>.ics`. A download that fails or is not valid iCalendar keeps the old file. Datascape never serves dotfiles, so the password in `.page-settings` cannot be downloaded. It is still in every backup of the wiki folder.
+
+The calendars page lists the maintenance tasks (repeat rule, last date, next date) and the sync status of each calendar.
+
 ## Quick-add bookmarklet
 
 Replace `wiki.host` and `/Topics/Bookmarks/` with your host and target page:

assets/calendar/page.html

@@ -0,0 +1,45 @@
+<h2 id="maintenance">Maintenance</h2>
+{{if .Maintenance}}
+<div class="cal-scroll"><table class="data-table panel cal-table">
+    <thead><tr><th>Task</th><th>Repeats</th><th>Last</th><th>Next</th></tr></thead>
+    <tbody>
+    {{range .Maintenance}}
+    <tr><td>{{.Summary}}</td><td class="muted">{{.Rule}}</td><td class="nowrap">{{.Last}}</td><td class="nowrap">{{.Next}}</td></tr>
+    {{end}}
+    </tbody>
+</table></div>
+{{else if .HasMaintenance}}
+<p class="muted">No maintenance tasks within a year of today.</p>
+{{else}}
+<p class="muted">No maintenance calendar. Set <code>maintenance = &lt;name&gt;</code> in this folder's <code>.page-settings</code>.</p>
+{{end}}
+
+<h2 id="calendars">Calendars</h2>
+{{if .Calendars}}
+<div class="cal-scroll"><table class="data-table panel cal-table">
+    <thead><tr><th>Calendar</th><th>Role</th><th>Events</th><th>Updated</th></tr></thead>
+    <tbody>
+    {{range .Calendars}}
+    <tr>
+        <td>{{.Name}}{{if .Error}}<div class="cal-error">{{.Error}}</div>{{end}}</td>
+        <td class="muted">{{.Roles}}</td>
+        <td>{{.Events}}</td>
+        <td class="nowrap">{{.Updated}}</td>
+    </tr>
+    {{end}}
+    </tbody>
+</table></div>
+{{else}}
+<p class="muted">No <code>.ics</code> files in this folder yet.</p>
+{{end}}
+{{if .IsSyncDir}}
+{{if .SyncEnabled}}
+<form class="cal-sync row" method="post" action="?calsync">
+    <button type="submit" class="btn">Sync now</button>
+    <span class="muted">{{if .LastRun}}Last sync: {{.LastRun}}{{else}}Not synced yet{{end}}</span>
+</form>
+{{if .LastError}}<p class="cal-error">{{.LastError}}</p>{{end}}
+{{else}}
+<p class="muted">Sync is off. Set <code>caldav-url</code>, <code>caldav-user</code> and <code>caldav-pass</code> in this folder's <code>.page-settings</code>.</p>
+{{end}}
+{{end}}

assets/calendar/widget.html

@@ -0,0 +1,16 @@
+<span class="dropdown maint">
+    <button type="button" class="btn maint-toggle{{if not .Count}} is-idle{{end}}" data-action="maint-menu" aria-haspopup="true" aria-expanded="false" title="Maintenance (H)">{{icon "maintenance"}}<span class="maint-count">{{.Count}}</span></button>
+    <div class="dropdown-menu align-right maint-menu">
+        <div class="panel-header">Today</div>
+        <div class="maint-list">
+            {{range .Today}}<span class="maint-when">{{.When}}</span><span>{{.Summary}}</span>
+            {{else}}<span class="muted">Nothing due</span>{{end}}
+        </div>
+        <div class="panel-header">Next 7 days</div>
+        <div class="maint-list">
+            {{range .Upcoming}}<span class="maint-when">{{.When}}</span><span>{{.Summary}}</span>
+            {{else}}<span class="muted">Nothing planned</span>{{end}}
+        </div>
+        {{if .PageURL}}<a class="btn btn-block maint-all" href="{{.PageURL}}">All maintenance →</a>{{end}}
+    </div>
+</span>

assets/diary/content.html

@@ -10,4 +10,8 @@
   {{end}}
 </div>
 {{end}}
+{{if or .Events .Weight}}<div class="diary-day-cal muted">
+{{if .Events}}<p>{{.Events}}</p>{{end}}
+{{if .Weight}}<p>{{.Weight}}</p>{{end}}
+</div>{{end}}
 {{end}}

assets/global-shortcuts.js

@@ -16,6 +16,12 @@
                 e.preventDefault();
                 if (window.location.pathname !== '/' && typeof movePage === 'function') movePage();
                 break;
+            case 'H':
+                var maint = document.querySelector('[data-action="maint-menu"]');
+                if (!maint) return;
+                e.preventDefault();
+                maint.click();
+                break;
             case 'F':
                 var input = document.querySelector('.search-input');
                 if (!input) return;
@@ -58,12 +64,14 @@ document.addEventListener('keydown', function (e) {
 });
 
 document.addEventListener('DOMContentLoaded', function () {
-  var trigger = document.querySelector('[data-action="actions-menu"]');
-  if (!trigger) return;
-  wireDropdown(trigger);
-  var menu = trigger.parentElement.querySelector('.dropdown-menu');
-  if (!menu) return;
-  trigger.addEventListener('click', function () {
-    trigger.setAttribute('aria-expanded', menu.classList.contains('is-open') ? true : false);
+  ['actions-menu', 'maint-menu'].forEach(function (action) {
+    var trigger = document.querySelector('[data-action="' + action + '"]');
+    if (!trigger) return;
+    wireDropdown(trigger);
+    var menu = trigger.parentElement.querySelector('.dropdown-menu');
+    if (!menu) return;
+    trigger.addEventListener('click', function () {
+      trigger.setAttribute('aria-expanded', menu.classList.contains('is-open') ? true : false);
+    });
   });
 });

assets/icons/delete.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="1em" height="1em"
+     fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="miter" stroke-linecap="square">
+  <path d="M2 4h12M6 4V2h4v2M4 4l1 10h6l1-10M7 7v4M9 7v4"/>
+</svg>

assets/icons/edit.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="1em" height="1em"
+     fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="miter" stroke-linecap="square">
+  <path d="M11 2l3 3-8 8H3v-3zM9 4l3 3"/>
+</svg>

assets/icons/maintenance.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="1em" height="1em"
+     fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="miter" stroke-linecap="square">
+  <path d="M2 3h12v11H2zM2 6h12M5 1v2M11 1v2M5 10l2 2 4-4"/>
+</svg>

assets/icons/move.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="1em" height="1em"
+     fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="miter" stroke-linecap="square">
+  <path d="M2 8h8M7 5l3 3-3 3M13 2v12"/>
+</svg>

assets/icons/new.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="1em" height="1em"
+     fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="miter" stroke-linecap="square">
+  <path d="M8 3v10M3 8h10"/>
+</svg>

assets/icons/rebuild.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="1em" height="1em"
+     fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="miter" stroke-linecap="square">
+  <path d="M13 8a5 5 0 1 1-1.5-3.5M12 1v4H8"/>
+</svg>

assets/icons/reveal.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="1em" height="1em"
+     fill="none" stroke="currentColor" stroke-width="1.5" stroke-linejoin="miter" stroke-linecap="square">
+  <path d="M1 14V3h5l1 2h8v9zM8 12V8M6 10l2-2 2 2"/>
+</svg>

assets/layout.html

@@ -31,6 +31,7 @@
             {{end}}
             <div class="header-actions row">
                 {{if .EditMode}}{{block "headerActions" .}}{{end}}{{else}}
+                {{maintenanceWidget}}
                 <span class="dropdown actions">
                     <button type="button" class="btn actions-toggle" data-action="actions-menu" aria-haspopup="true" aria-expanded="false" title="Actions">ACTIONS</button>
                     <div class="dropdown-menu align-right actions-menu">

assets/page/main.html

@@ -1,13 +1,13 @@
 {{define "headScripts"}}<script src="/_/page/actions.js"></script>{{end}}
 
 {{define "headerActions"}}{{if .CanEdit}}
-<button class="btn btn-block" onclick="newPage()" title="New page (N)">NEW</button>
-<button class="btn btn-block" data-companion-reveal hidden title="Reveal in file manager">REVEAL</button>
+<button class="btn btn-block" onclick="newPage()" title="New page (N)"><span class="btn-icon">{{icon "new"}}</span><span class="btn-label">NEW</span></button>
+<button class="btn btn-block" data-companion-reveal hidden title="Reveal in file manager"><span class="btn-icon">{{icon "reveal"}}</span><span class="btn-label">REVEAL</span></button>
 {{if not .IsRoot}}
-<button class="btn btn-block" onclick="movePage()" title="Move page (M)">MOVE</button>
-<button class="btn btn-block danger" onclick="deletePage()" title="Delete page">DELETE</button>
+<button class="btn btn-block" onclick="movePage()" title="Move page (M)"><span class="btn-icon">{{icon "move"}}</span><span class="btn-label">MOVE</span></button>
+<button class="btn btn-block danger" onclick="deletePage()" title="Delete page"><span class="btn-icon">{{icon "delete"}}</span><span class="btn-label">DELETE</span></button>
 {{end}}
-<a class="btn btn-block" href="?edit" title="Edit page (E)">EDIT</a>
+<a class="btn btn-block" href="?edit" title="Edit page (E)"><span class="btn-icon">{{icon "edit"}}</span><span class="btn-label">EDIT</span></a>
 {{end}}{{end}}
 
 {{define "content"}}

assets/search/main.html

@@ -43,7 +43,7 @@
 {{end}}
 
 {{define "headerActions"}}
-<button class="btn btn-block" onclick="rebuildIndex()" title="Rebuild search index">REBUILD INDEX</button>
+<button class="btn btn-block" onclick="rebuildIndex()" title="Rebuild search index"><span class="btn-icon">{{icon "rebuild"}}</span><span class="btn-label">REBUILD INDEX</span></button>
 {{end}}
 
 {{define "footerExtras"}}

assets/style.css

@@ -389,6 +389,10 @@ main > h2 {
 .dropdown-menu.scrollable { max-height: 23rem; overflow-y: auto; }
 
 .actions-special > .btn {text-align: left;}
+/* Header actions carry an icon and a label: the mobile dropdown shows the
+   label, the inline desktop bar (see responsive block) the icon. */
+.btn-icon { display: none; }
+.btn-icon svg { display: block; }
 
 /* === Suggestion dropdown (header search + editor link picker) ===
    Anchored to a position:relative host. Mirrors .dropdown-menu visuals with
@@ -797,6 +801,37 @@ aside.sidebar:empty { display: none; }
 .diary-cal-grid td.cal-current,
 .diary-cal-grid td.cal-current a { color: var(--primary-hover); }
 .btn-block.cal-current { color: var(--primary-hover); }
+/* Calendar events and weight under a diary day heading. */
+.diary-day-cal { margin: var(--space-3) 0 0; }
+.diary-day-cal p { margin: 0; }
+
+/* === Calendars ===
+   Header maintenance chip + dropdown, and the calendars folder page. */
+.maint-toggle { display: inline-flex; align-items: center; }
+.maint-count { margin-left: 0.3rem; }
+.maint-toggle.is-idle { color: var(--text-muted); }
+.maint-menu {
+    min-width: 20rem;
+    max-width: calc(100vw - 2rem);
+    padding: var(--space-2) var(--space-3);
+    white-space: normal;
+}
+/* Two columns so dates line up; an empty when-cell keeps the grid intact. */
+.maint-list {
+    display: grid;
+    grid-template-columns: max-content 1fr;
+    column-gap: var(--space-2);
+    row-gap: 0.15rem;
+    font-size: var(--font-sm);
+}
+.maint-list > .muted { grid-column: 1 / -1; }
+.maint-list + .panel-header { margin-top: var(--space-3); }
+.maint-when { color: var(--text-muted); white-space: nowrap; }
+.maint-all { margin-top: var(--space-3); padding: 0.3rem 0 0; border-top: var(--border-dashed); }
+.cal-scroll { overflow-x: auto; }
+.cal-table .nowrap { white-space: nowrap; }
+.cal-error { color: var(--danger); font-size: var(--font-sm); }
+.cal-sync { margin-top: var(--space-3); }
 
 /* === Fitness dashboard ===
    Server-rendered inline SVG charts. Geometry comes precomputed from Go;
@@ -840,7 +875,9 @@ aside.sidebar:empty { display: none; }
 @media (min-width: 1101px) {
     .actions-toggle, .actions-special {display: none;}
     .actions, .actions-menu, .actions.dropdown-menu.is-open {display: contents;}
-    .actions-menu .btn-block { width: auto; padding: 0;}
+    .actions-menu .btn-block { width: auto; padding: 0; align-items: center; }
+    .actions-menu .btn-icon { display: inline-block; }
+    .actions-menu .btn-label { display: none; }
 }
 
 @media (max-width: 600px) {

calendar.go

@@ -0,0 +1,666 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/emersion/go-ical"
+	"github.com/teambition/rrule-go"
+)
+
+// calendarsDir is the absolute path of the calendars folder (-calendars).
+// Empty disables the diary lines, the maintenance widget and the sync. Every
+// calendar is one <Name>.ics file in this folder; the folder's .page-settings
+// assigns calendars to roles and holds the CalDAV sync credentials.
+var calendarsDir string
+
+// === Settings ===
+
+type calendarSettings struct {
+	// Roles: calendar names (file basenames without .ics).
+	Diary       []string
+	Weight      []string
+	Maintenance []string
+
+	CaldavURL    string
+	CaldavUser   string
+	CaldavPass   string
+	SyncInterval time.Duration // 0 = startup and manual only
+}
+
+// readCalendarSettings reads the calendar keys from dir's .page-settings.
+// Read on every use, so edits apply without a restart.
+func readCalendarSettings(dir string) calendarSettings {
+	kv := readSettingsFile(dir)
+	s := calendarSettings{
+		Diary:        splitCalendarList(kv["diary"]),
+		Weight:       splitCalendarList(kv["weight"]),
+		Maintenance:  splitCalendarList(kv["maintenance"]),
+		CaldavURL:    kv["caldav-url"],
+		CaldavUser:   kv["caldav-user"],
+		CaldavPass:   kv["caldav-pass"],
+		SyncInterval: 15 * time.Minute,
+	}
+	if v, ok := kv["sync-interval"]; ok {
+		if d, err := time.ParseDuration(v); err == nil && d >= 0 {
+			s.SyncInterval = d
+		}
+	}
+	return s
+}
+
+func splitCalendarList(v string) []string {
+	var out []string
+	for _, name := range strings.Split(v, ",") {
+		if name = strings.TrimSpace(name); name != "" {
+			out = append(out, name)
+		}
+	}
+	return out
+}
+
+// calendarPath returns the file of calendar name in dir, or "" when the name
+// would escape the folder.
+func calendarPath(dir, name string) string {
+	if name == "" || strings.ContainsAny(name, `/\`) || strings.HasPrefix(name, ".") {
+		return ""
+	}
+	return filepath.Join(dir, name+".ics")
+}
+
+// === Model ===
+
+// calEvent is one expanded occurrence.
+type calEvent struct {
+	Calendar string
+	UID      string
+	Summary  string
+	Start    time.Time // local time; all-day events start at local midnight
+	End      time.Time // exclusive
+	AllDay   bool
+	Stamp    time.Time  // LAST-MODIFIED, else DTSTAMP
+	Series   *calSeries // nil for single events
+}
+
+// calSeries describes a recurring event as a whole.
+type calSeries struct {
+	Calendar string
+	UID      string
+	Summary  string
+	Rule     string // human-readable, e.g. "every 2 weeks (Sa)"
+}
+
+// calItem is a parsed VEVENT: a single event, a recurring master, or a
+// RECURRENCE-ID override attached to its master.
+type calItem struct {
+	uid       string
+	summary   string
+	start     time.Time
+	end       time.Time
+	allDay    bool
+	days      int // all-day length in days; keeps occurrences DST-safe
+	stamp     time.Time
+	cancelled bool
+
+	set       *rrule.Set         // nil = single event
+	series    *calSeries         // set together with set
+	overrides map[int64]*calItem // RECURRENCE-ID (unix) → replacement
+}
+
+// calFile is one parsed calendar file.
+type calFile struct {
+	modTime time.Time
+	size    int64
+	items   []*calItem
+	events  int // VEVENT components in the file
+}
+
+// === Store ===
+
+// calStore caches parsed calendar files by path. An entry is reused while the
+// file's modtime and size are unchanged, so a request costs one stat per
+// calendar. Parsed files are never mutated, so callers may keep using a
+// snapshot after the lock is released.
+var calStore = struct {
+	sync.Mutex
+	files map[string]*calFile
+}{files: map[string]*calFile{}}
+
+// loadCalendar returns the parsed calendar at path; nil when it does not exist
+// or cannot be parsed (logged).
+func loadCalendar(path string) *calFile {
+	info, err := os.Stat(path)
+	if err != nil {
+		return nil
+	}
+	calStore.Lock()
+	defer calStore.Unlock()
+	if f := calStore.files[path]; f != nil && f.modTime.Equal(info.ModTime()) && f.size == info.Size() {
+		return f
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil
+	}
+	f, err := parseCalendar(filepath.Base(path), data)
+	if err != nil {
+		log.Printf("calendar %s: %v", path, err)
+		delete(calStore.files, path)
+		return nil
+	}
+	f.modTime = info.ModTime()
+	f.size = info.Size()
+	calStore.files[path] = f
+	return f
+}
+
+// calendarOccurrences expands every event of the named calendars in dir that
+// overlaps [from, to). The result is sorted by start, then summary.
+func calendarOccurrences(dir string, names []string, from, to time.Time) []calEvent {
+	var out []calEvent
+	for _, name := range names {
+		p := calendarPath(dir, name)
+		if p == "" {
+			continue
+		}
+		f := loadCalendar(p)
+		if f == nil {
+			continue
+		}
+		for _, it := range f.items {
+			out = it.expand(name, from, to, out)
+		}
+	}
+	sort.SliceStable(out, func(i, j int) bool {
+		if !out[i].Start.Equal(out[j].Start) {
+			return out[i].Start.Before(out[j].Start)
+		}
+		return out[i].Summary < out[j].Summary
+	})
+	return out
+}
+
+func (it *calItem) occurrence(calendar string, start, end time.Time) calEvent {
+	return calEvent{
+		Calendar: calendar,
+		UID:      it.uid,
+		Summary:  it.summary,
+		Start:    start.In(time.Local),
+		End:      end.In(time.Local),
+		AllDay:   it.allDay,
+		Stamp:    it.stamp,
+	}
+}
+
+// overlaps reports whether [start, end) intersects [from, to). Zero-length
+// events count when they start inside the window.
+func overlaps(start, end, from, to time.Time) bool {
+	if !start.Before(to) {
+		return false
+	}
+	return end.After(from) || !start.Before(from)
+}
+
+// expand appends the item's occurrences in [from, to) to out.
+func (it *calItem) expand(calendar string, from, to time.Time, out []calEvent) []calEvent {
+	if it.cancelled {
+		return out
+	}
+	if it.set == nil {
+		if overlaps(it.start, it.end, from, to) {
+			out = append(out, it.occurrence(calendar, it.start, it.end))
+		}
+		return out
+	}
+	// Start the search early enough to catch occurrences that began before
+	// the window but still run into it.
+	after := from.Add(-it.end.Sub(it.start)).Add(-48 * time.Hour)
+	for _, s := range it.set.Between(after, to, true) {
+		if _, overridden := it.overrides[s.Unix()]; overridden {
+			continue
+		}
+		e := it.occurrenceEnd(s)
+		if overlaps(s, e, from, to) {
+			ev := it.occurrence(calendar, s, e)
+			ev.Series = it.series
+			out = append(out, ev)
+		}
+	}
+	// Overrides are placed on their own dates: a moved occurrence can enter
+	// or leave the window independently of its original slot.
+	for _, o := range it.overrides {
+		if o.cancelled || !overlaps(o.start, o.end, from, to) {
+			continue
+		}
+		ev := o.occurrence(calendar, o.start, o.end)
+		ev.Series = it.series
+		out = append(out, ev)
+	}
+	return out
+}
+
+// occurrenceEnd returns the end of the occurrence starting at s.
+func (it *calItem) occurrenceEnd(s time.Time) time.Time {
+	if it.allDay {
+		return s.AddDate(0, 0, it.days)
+	}
+	return s.Add(it.end.Sub(it.start))
+}
+
+// === Parsing ===
+
+// calParser holds per-file parse state: the file name for log messages, the
+// TZIDs already warned about, and resolved locations.
+type calParser struct {
+	file   string
+	zones  map[string]*time.Location
+	warned map[string]bool
+}
+
+func parseCalendar(file string, data []byte) (*calFile, error) {
+	data = bytes.TrimPrefix(data, []byte{0xEF, 0xBB, 0xBF}) // UTF-8 BOM
+	cal, err := ical.NewDecoder(bytes.NewReader(data)).Decode()
+	if err != nil {
+		return nil, err
+	}
+	p := &calParser{file: file, zones: map[string]*time.Location{}, warned: map[string]bool{}}
+	f := &calFile{}
+	masters := map[string]*calItem{}
+	type override struct {
+		item    *calItem
+		recurID time.Time
+	}
+	var overrides []override
+	for _, comp := range cal.Children {
+		if comp.Name != ical.CompEvent {
+			continue
+		}
+		f.events++
+		it, recurID, err := p.item(comp)
+		if err != nil {
+			continue
+		}
+		if !recurID.IsZero() {
+			overrides = append(overrides, override{it, recurID})
+			continue
+		}
+		f.items = append(f.items, it)
+		if it.uid != "" {
+			masters[it.uid] = it
+		}
+	}
+	// Overrides can come before their master in the file, so attach them in
+	// a second pass. One without a recurring master is shown as a single event.
+	for _, o := range overrides {
+		m := masters[o.item.uid]
+		if m == nil || m.set == nil {
+			f.items = append(f.items, o.item)
+			continue
+		}
+		if o.item.summary == "" {
+			o.item.summary = m.summary
+		}
+		m.overrides[o.recurID.Unix()] = o.item
+	}
+	return f, nil
+}
+
+// item parses one VEVENT. recurID is non-zero for RECURRENCE-ID overrides.
+func (p *calParser) item(comp *ical.Component) (it *calItem, recurID time.Time, err error) {
+	startProp := comp.Props.Get(ical.PropDateTimeStart)
+	if startProp == nil {
+		return nil, time.Time{}, errors.New("no DTSTART")
+	}
+	starts, allDay, err := p.times(startProp)
+	if err != nil || len(starts) == 0 {
+		return nil, time.Time{}, fmt.Errorf("DTSTART: %v", err)
+	}
+	it = &calItem{start: starts[0], allDay: allDay}
+	it.uid = calText(comp.Props.Get(ical.PropUID))
+	it.summary = strings.TrimSpace(calText(comp.Props.Get(ical.PropSummary)))
+
+	it.end = it.start
+	if prop := comp.Props.Get(ical.PropDateTimeEnd); prop != nil {
+		if ends, _, err := p.times(prop); err == nil && len(ends) > 0 {
+			it.end = ends[0]
+		}
+	} else if prop := comp.Props.Get(ical.PropDuration); prop != nil {
+		if d, err := prop.Duration(); err == nil {
+			if allDay {
+				it.end = it.start.AddDate(0, 0, int(math.Round(d.Hours()/24)))
+			} else {
+				it.end = it.start.Add(d)
+			}
+		}
+	} else if allDay {
+		it.end = it.start.AddDate(0, 0, 1)
+	}
+	if it.end.Before(it.start) {
+		it.end = it.start
+	}
+	if allDay {
+		it.days = calendarDaysBetween(it.start, it.end)
+		if it.days < 1 {
+			it.days = 1
+		}
+		it.end = it.start.AddDate(0, 0, it.days)
+	}
+
+	if strings.EqualFold(calText(comp.Props.Get(ical.PropStatus)), "CANCELLED") {
+		it.cancelled = true
+	}
+	for _, name := range []string{ical.PropLastModified, ical.PropDateTimeStamp} {
+		if prop := comp.Props.Get(name); prop != nil {
+			if ts, _, err := p.times(prop); err == nil && len(ts) > 0 {
+				it.stamp = ts[0]
+				break
+			}
+		}
+	}
+
+	if prop := comp.Props.Get(ical.PropRecurrenceID); prop != nil {
+		ids, _, err := p.times(prop)
+		if err != nil || len(ids) == 0 {
+			return nil, time.Time{}, fmt.Errorf("RECURRENCE-ID: %v", err)
+		}
+		return it, ids[0], nil
+	}
+
+	rule := comp.Props.Get(ical.PropRecurrenceRule)
+	rdates := comp.Props.Values(ical.PropRecurrenceDates)
+	if rule == nil && len(rdates) == 0 {
+		return it, time.Time{}, nil
+	}
+	set := &rrule.Set{}
+	ruleText := ""
+	if rule != nil {
+		opt, err := rrule.StrToROptionInLocation(rule.Value, it.start.Location())
+		if err != nil {
+			p.warn("rrule:"+rule.Value, "cannot parse RRULE %q of %q: %v", rule.Value, it.summary, err)
+			return it, time.Time{}, nil
+		}
+		opt.Dtstart = it.start
+		r, err := rrule.NewRRule(*opt)
+		if err != nil {
+			p.warn("rrule:"+rule.Value, "cannot build RRULE %q of %q: %v", rule.Value, it.summary, err)
+			return it, time.Time{}, nil
+		}
+		set.RRule(r)
+		ruleText = describeRRule(opt)
+	} else {
+		// Without an RRULE the set only holds RDATEs; DTSTART is always the
+		// first occurrence.
+		set.RDate(it.start)
+		ruleText = "on selected dates"
+	}
+	for i := range rdates {
+		if ts, _, err := p.times(&rdates[i]); err == nil {
+			for _, t := range ts {
+				set.RDate(t)
+			}
+		}
+	}
+	for _, prop := range comp.Props.Values(ical.PropExceptionDates) {
+		if ts, _, err := p.times(&prop); err == nil {
+			for _, t := range ts {
+				set.ExDate(t)
+			}
+		}
+	}
+	it.set = set
+	it.overrides = map[int64]*calItem{}
+	it.series = &calSeries{
+		Calendar: strings.TrimSuffix(p.file, ".ics"),
+		UID:      it.uid,
+		Summary:  it.summary,
+		Rule:     ruleText,
+	}
+	return it, time.Time{}, nil
+}
+
+// calText unescapes a TEXT value. Unlike go-ical's Text it keeps unescaped
+// commas: clients write titles like "95,6kg" without the required backslash,
+// and go-ical would cut them at the comma. Unknown escapes are kept as is.
+func calText(prop *ical.Prop) string {
+	if prop == nil {
+		return ""
+	}
+	v := prop.Value
+	if !strings.Contains(v, `\`) {
+		return v
+	}
+	var sb strings.Builder
+	for i := 0; i < len(v); i++ {
+		c := v[i]
+		if c != '\\' || i+1 == len(v) {
+			sb.WriteByte(c)
+			continue
+		}
+		i++
+		switch n := v[i]; n {
+		case 'n', 'N':
+			sb.WriteByte('\n')
+		case '\\', ';', ',':
+			sb.WriteByte(n)
+		default:
+			sb.WriteByte('\\')
+			sb.WriteByte(n)
+		}
+	}
+	return sb.String()
+}
+
+// times parses a DATE or DATE-TIME property. Comma-separated lists (EXDATE,
+// RDATE) yield several values. Dates and floating times use the local zone; an
+// unknown TZID falls back to it with a warning.
+func (p *calParser) times(prop *ical.Prop) ([]time.Time, bool, error) {
+	loc := time.Local
+	if tzid := prop.Params.Get(ical.PropTimezoneID); tzid != "" {
+		loc = p.zone(tzid)
+	}
+	var out []time.Time
+	allDay := false
+	for _, v := range strings.Split(prop.Value, ",") {
+		v = strings.TrimSpace(v)
+		var t time.Time
+		var err error
+		switch {
+		case len(v) == 8:
+			t, err = time.ParseInLocation("20060102", v, time.Local)
+			allDay = true
+		case len(v) == 16 && strings.HasSuffix(v, "Z"):
+			t, err = time.Parse("20060102T150405Z", v)
+		case len(v) == 15:
+			t, err = time.ParseInLocation("20060102T150405", v, loc)
+		default:
+			err = fmt.Errorf("unsupported value %q", v)
+		}
+		if err != nil {
+			return nil, false, err
+		}
+		out = append(out, t)
+	}
+	return out, allDay, nil
+}
+
+func (p *calParser) zone(tzid string) *time.Location {
+	if loc, ok := p.zones[tzid]; ok {
+		return loc
+	}
+	loc, err := time.LoadLocation(tzid)
+	if err != nil {
+		// Some clients prefix the IANA name, e.g.
+		// "/freeassociation.sourceforge.net/Tzfile/Europe/Berlin".
+		parts := strings.Split(strings.Trim(tzid, "/"), "/")
+		if len(parts) >= 2 {
+			loc, err = time.LoadLocation(strings.Join(parts[len(parts)-2:], "/"))
+		}
+	}
+	if err != nil {
+		p.warn("tz:"+tzid, "unknown TZID %q, using local time", tzid)
+		loc = time.Local
+	}
+	p.zones[tzid] = loc
+	return loc
+}
+
+func (p *calParser) warn(key, format string, args ...any) {
+	if p.warned[key] {
+		return
+	}
+	p.warned[key] = true
+	log.Printf("calendar %s: "+format, append([]any{p.file}, args...)...)
+}
+
+// calendarDaysBetween counts calendar days from a to b (both local midnights),
+// independent of DST shifts.
+func calendarDaysBetween(a, b time.Time) int {
+	ay, am, ad := a.Date()
+	by, bm, bd := b.Date()
+	ua := time.Date(ay, am, ad, 0, 0, 0, 0, time.UTC)
+	ub := time.Date(by, bm, bd, 0, 0, 0, 0, time.UTC)
+	return int(ub.Sub(ua).Hours() / 24)
+}
+
+// === Formatting ===
+
+var germanWeekdays = [...]string{"So", "Mo", "Di", "Mi", "Do", "Fr", "Sa"}
+
+// calDayLabel formats a date as "Sa 27.09.".
+func calDayLabel(t time.Time) string {
+	return fmt.Sprintf("%s %02d.%02d.", germanWeekdays[t.Weekday()], t.Day(), int(t.Month()))
+}
+
+// describeRRule turns common rules into short text ("weekly (Mo)",
+// "every 2 weeks (Sa)", "monthly (day 1)"). Anything with parts it does not
+// know falls back to the raw rule.
+func describeRRule(opt *rrule.ROption) string {
+	if len(opt.Bysetpos) > 0 || len(opt.Byyearday) > 0 || len(opt.Byweekno) > 0 ||
+		len(opt.Byhour) > 0 || len(opt.Byminute) > 0 || len(opt.Bysecond) > 0 {
+		return opt.RRuleString()
+	}
+	units := map[rrule.Frequency][2]string{
+		rrule.DAILY:   {"daily", "days"},
+		rrule.WEEKLY:  {"weekly", "weeks"},
+		rrule.MONTHLY: {"monthly", "months"},
+		rrule.YEARLY:  {"yearly", "years"},
+	}
+	u, ok := units[opt.Freq]
+	if !ok {
+		return opt.RRuleString()
+	}
+	text := u[0]
+	if opt.Interval > 1 {
+		text = fmt.Sprintf("every %d %s", opt.Interval, u[1])
+	}
+	var details []string
+	for _, wd := range opt.Byweekday {
+		name := germanWeekdays[(wd.Day()+1)%7]
+		if n := wd.N(); n != 0 {
+			name = strconv.Itoa(n) + ". " + name
+			if n == -1 {
+				name = "last " + germanWeekdays[(wd.Day()+1)%7]
+			}
+		}
+		details = append(details, name)
+	}
+	for _, d := range opt.Bymonthday {
+		details = append(details, fmt.Sprintf("day %d", d))
+	}
+	for _, m := range opt.Bymonth {
+		if m >= 1 && m <= 12 {
+			details = append(details, germanMonths[time.Month(m)])
+		}
+	}
+	if len(details) > 0 {
+		text += " (" + strings.Join(details, ", ") + ")"
+	}
+	return text
+}
+
+// === Diary lines ===
+
+// calDayLines is the calendar content shown under a diary day.
+type calDayLines struct {
+	Events string // "Feiertag, 10:00 Brunch, 19:30 Kino"
+	Weight string // "95,6 kg"
+}
+
+var weightTitle = regexp.MustCompile(`(?i)^\s*(\d+(?:[.,]\d+)?)\s*kg\s*$`)
+
+// calendarDayLines builds the diary lines for every day in [from, to), keyed
+// by "YYYY-MM-DD". Events come from the diary role, weights from the weight
+// role. Days without either are absent.
+func calendarDayLines(from, to time.Time) map[string]calDayLines {
+	out := map[string]calDayLines{}
+	if calendarsDir == "" {
+		return out
+	}
+	s := readCalendarSettings(calendarsDir)
+
+	type dayEvents struct{ allDay, timed []calEvent }
+	byDay := map[string]*dayEvents{}
+	for _, ev := range calendarOccurrences(calendarsDir, s.Diary, from, to) {
+		if ev.AllDay {
+			// Multi-day all-day events show on every day they cover.
+			for d := ev.Start; d.Before(ev.End); d = d.AddDate(0, 0, 1) {
+				key := d.Format("2006-01-02")
+				if byDay[key] == nil {
+					byDay[key] = &dayEvents{}
+				}
+				byDay[key].allDay = append(byDay[key].allDay, ev)
+			}
+			continue
+		}
+		key := ev.Start.Format("2006-01-02")
+		if byDay[key] == nil {
+			byDay[key] = &dayEvents{}
+		}
+		byDay[key].timed = append(byDay[key].timed, ev)
+	}
+	for key, d := range byDay {
+		sort.SliceStable(d.allDay, func(i, j int) bool { return d.allDay[i].Summary < d.allDay[j].Summary })
+		var parts []string
+		for _, ev := range d.allDay {
+			if ev.Summary != "" {
+				parts = append(parts, ev.Summary)
+			}
+		}
+		// Timed events are already sorted by start, then summary.
+		for _, ev := range d.timed {
+			parts = append(parts, strings.TrimSpace(ev.Start.Format("15:04")+" "+ev.Summary))
+		}
+		if len(parts) > 0 {
+			out[key] = calDayLines{Events: strings.Join(parts, ", ")}
+		}
+	}
+
+	stamps := map[string]time.Time{}
+	for _, ev := range calendarOccurrences(calendarsDir, s.Weight, from, to) {
+		m := weightTitle.FindStringSubmatch(ev.Summary)
+		if m == nil {
+			continue
+		}
+		key := ev.Start.Format("2006-01-02")
+		// Several entries on one day: the last edited one wins.
+		if prev, ok := stamps[key]; ok && ev.Stamp.Before(prev) {
+			continue
+		}
+		stamps[key] = ev.Stamp
+		lines := out[key]
+		lines.Weight = strings.ReplaceAll(m[1], ".", ",") + " kg"
+		out[key] = lines
+	}
+	return out
+}

calendar_test.go

@@ -0,0 +1,283 @@
+package main
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+// writeCal writes a VCALENDAR with the given VEVENT bodies to dir/name.ics.
+func writeCal(t *testing.T, dir, name string, events ...string) {
+	t.Helper()
+	var b strings.Builder
+	b.WriteString("BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:test\r\n")
+	for _, ev := range events {
+		b.WriteString("BEGIN:VEVENT\r\n")
+		for _, line := range strings.Split(strings.TrimSpace(ev), "\n") {
+			b.WriteString(strings.TrimSpace(line) + "\r\n")
+		}
+		b.WriteString("END:VEVENT\r\n")
+	}
+	b.WriteString("END:VCALENDAR\r\n")
+	if err := os.WriteFile(filepath.Join(dir, name+".ics"), []byte(b.String()), 0644); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func withBerlin(t *testing.T) {
+	t.Helper()
+	loc, err := time.LoadLocation("Europe/Berlin")
+	if err != nil {
+		t.Fatal(err)
+	}
+	prev := time.Local
+	time.Local = loc
+	t.Cleanup(func() { time.Local = prev })
+}
+
+func day(y int, m time.Month, d int) time.Time {
+	return time.Date(y, m, d, 0, 0, 0, 0, time.Local)
+}
+
+func summaries(evs []calEvent) []string {
+	var out []string
+	for _, ev := range evs {
+		out = append(out, ev.Start.Format("2006-01-02 15:04")+" "+ev.Summary)
+	}
+	return out
+}
+
+func assertStrings(t *testing.T, got, want []string) {
+	t.Helper()
+	if strings.Join(got, "\n") != strings.Join(want, "\n") {
+		t.Fatalf("got:\n  %s\nwant:\n  %s", strings.Join(got, "\n  "), strings.Join(want, "\n  "))
+	}
+}
+
+func TestCalendarSingleAndAllDay(t *testing.T) {
+	withBerlin(t)
+	dir := t.TempDir()
+	writeCal(t, dir, "P",
+		`UID:a
+		SUMMARY:Zahnarzt
+		DTSTART;TZID=Europe/Berlin:20261002T090000
+		DTEND;TZID=Europe/Berlin:20261002T100000`,
+		`UID:b
+		SUMMARY:Urlaub
+		DTSTART;VALUE=DATE:20261001
+		DTEND;VALUE=DATE:20261004`,
+		`UID:c
+		SUMMARY:UTC call
+		DTSTART:20261002T160000Z
+		DURATION:PT1H`,
+	)
+	got := summaries(calendarOccurrences(dir, []string{"P"}, day(2026, 10, 2), day(2026, 10, 3)))
+	assertStrings(t, got, []string{
+		"2026-10-01 00:00 Urlaub",
+		"2026-10-02 09:00 Zahnarzt",
+		"2026-10-02 18:00 UTC call",
+	})
+	// DTEND of all-day events is exclusive.
+	if got := calendarOccurrences(dir, []string{"P"}, day(2026, 10, 4), day(2026, 10, 5)); len(got) != 0 {
+		t.Fatalf("all-day event leaked past DTEND: %v", summaries(got))
+	}
+}
+
+func TestCalendarRecurrence(t *testing.T) {
+	withBerlin(t)
+	dir := t.TempDir()
+	writeCal(t, dir, "M",
+		`UID:backup
+		SUMMARY:Backup
+		DTSTART;TZID=Europe/Berlin:20260907T030000
+		DTEND;TZID=Europe/Berlin:20260907T040000
+		RRULE:FREQ=WEEKLY;BYDAY=MO
+		EXDATE;TZID=Europe/Berlin:20260914T030000,20260921T030000`,
+		`UID:backup
+		RECURRENCE-ID;TZID=Europe/Berlin:20260928T030000
+		SUMMARY:Backup (moved)
+		DTSTART;TZID=Europe/Berlin:20260929T050000
+		DTEND;TZID=Europe/Berlin:20260929T060000`,
+		`UID:backup
+		RECURRENCE-ID;TZID=Europe/Berlin:20261005T030000
+		DTSTART;TZID=Europe/Berlin:20261005T030000
+		STATUS:CANCELLED`,
+		`UID:sheets
+		SUMMARY:Bettwäsche
+		DTSTART;VALUE=DATE:20260905
+		RRULE:FREQ=WEEKLY;INTERVAL=2`,
+	)
+	got := summaries(calendarOccurrences(dir, []string{"M"}, day(2026, 9, 1), day(2026, 10, 20)))
+	assertStrings(t, got, []string{
+		"2026-09-05 00:00 Bettwäsche",
+		"2026-09-07 03:00 Backup",
+		"2026-09-19 00:00 Bettwäsche",
+		"2026-09-29 05:00 Backup (moved)",
+		"2026-10-03 00:00 Bettwäsche",
+		"2026-10-12 03:00 Backup",
+		"2026-10-17 00:00 Bettwäsche",
+		"2026-10-19 03:00 Backup",
+	})
+	// Wall-clock time survives the DST change on 2026-10-25.
+	got = summaries(calendarOccurrences(dir, []string{"M"}, day(2026, 10, 26), day(2026, 10, 27)))
+	assertStrings(t, got, []string{"2026-10-26 03:00 Backup"})
+
+	evs := calendarOccurrences(dir, []string{"M"}, day(2026, 9, 5), day(2026, 9, 8))
+	if evs[0].Series == nil || evs[0].Series.Rule != "every 2 weeks" {
+		t.Fatalf("sheets rule = %+v", evs[0].Series)
+	}
+	if evs[1].Series == nil || evs[1].Series.Rule != "weekly (Mo)" {
+		t.Fatalf("backup rule = %+v", evs[1].Series)
+	}
+}
+
+func TestCalendarUnknownTZIDFallsBack(t *testing.T) {
+	withBerlin(t)
+	dir := t.TempDir()
+	writeCal(t, dir, "P",
+		`UID:x
+		SUMMARY:Windows zone
+		DTSTART;TZID=W. Europe Standard Time:20261002T090000
+		DTEND;TZID=W. Europe Standard Time:20261002T100000`,
+		`UID:y
+		SUMMARY:Prefixed zone
+		DTSTART;TZID=/freeassociation.sourceforge.net/Tzfile/Europe/Berlin:20261002T110000`,
+	)
+	got := summaries(calendarOccurrences(dir, []string{"P"}, day(2026, 10, 2), day(2026, 10, 3)))
+	assertStrings(t, got, []string{
+		"2026-10-02 09:00 Windows zone",
+		"2026-10-02 11:00 Prefixed zone",
+	})
+}
+
+func TestCalendarDayLines(t *testing.T) {
+	withBerlin(t)
+	dir := t.TempDir()
+	prev := calendarsDir
+	calendarsDir = dir
+	t.Cleanup(func() { calendarsDir = prev })
+
+	if err := os.WriteFile(filepath.Join(dir, ".page-settings"),
+		[]byte("type = calendars\ndiary = Personal, Feiertage\nweight = Gewicht\nmaintenance = Maintainance\n"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	writeCal(t, dir, "Personal",
+		`UID:1
+		SUMMARY:Kino
+		DTSTART;TZID=Europe/Berlin:20261003T193000`,
+		`UID:2
+		SUMMARY:Brunch\, Anna
+		DTSTART;TZID=Europe/Berlin:20261003T100000`,
+	)
+	writeCal(t, dir, "Feiertage",
+		`UID:3
+		SUMMARY:Tag der Deutschen Einheit
+		DTSTART;VALUE=DATE:20261003`,
+	)
+	writeCal(t, dir, "Gewicht",
+		`UID:4
+		SUMMARY:95.9 KG
+		DTSTART;VALUE=DATE:20261003
+		DTSTAMP:20261003T060000Z`,
+		`UID:5
+		SUMMARY:95,6kg
+		DTSTART;VALUE=DATE:20261003
+		DTSTAMP:20261003T070000Z`,
+		`UID:6
+		SUMMARY:not a weight
+		DTSTART;VALUE=DATE:20261004`,
+	)
+	writeCal(t, dir, "Maintainance",
+		`UID:7
+		SUMMARY:Backup
+		DTSTART;VALUE=DATE:20261003`,
+	)
+
+	lines := calendarDayLines(day(2026, 10, 1), day(2026, 10, 10))
+	want := calDayLines{
+		Events: "Tag der Deutschen Einheit, 10:00 Brunch, Anna, 19:30 Kino",
+		Weight: "95,6 kg",
+	}
+	if lines["2026-10-03"] != want {
+		t.Fatalf("got %+v, want %+v", lines["2026-10-03"], want)
+	}
+	if _, ok := lines["2026-10-04"]; ok {
+		t.Fatalf("unparsable weight produced a line: %+v", lines["2026-10-04"])
+	}
+}
+
+func TestCalendarSync(t *testing.T) {
+	dir := t.TempDir()
+	prev := calendarsDir
+	calendarsDir = dir
+	t.Cleanup(func() { calendarsDir = prev })
+
+	ics := "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nBEGIN:VEVENT\r\nUID:1\r\nSUMMARY:95,6kg\r\nDTSTART;VALUE=DATE:20261003\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if u, p, _ := r.BasicAuth(); u != "me" || p != "secret" {
+			w.WriteHeader(http.StatusUnauthorized)
+			return
+		}
+		switch {
+		case r.Method == "PROPFIND" && r.URL.Path == "/dav/calendars/me/":
+			w.WriteHeader(http.StatusMultiStatus)
+			io.WriteString(w, `<?xml version="1.0"?>
+<d:multistatus xmlns:d="DAV:" xmlns:cal="urn:ietf:params:xml:ns:caldav">
+ <d:response><d:href>/dav/calendars/me/</d:href><d:propstat><d:prop><d:resourcetype><d:collection/></d:resourcetype></d:prop><d:status>HTTP/1.1 200 OK</d:status></d:propstat></d:response>
+ <d:response><d:href>/dav/calendars/me/gewicht/</d:href><d:propstat><d:prop><d:displayname>Gewicht</d:displayname><d:resourcetype><d:collection/><cal:calendar/></d:resourcetype></d:prop><d:status>HTTP/1.1 200 OK</d:status></d:propstat></d:response>
+ <d:response><d:href>/dav/calendars/me/broken/</d:href><d:propstat><d:prop><d:displayname>Broken/Name</d:displayname><d:resourcetype><d:collection/><cal:calendar/></d:resourcetype></d:prop><d:status>HTTP/1.1 200 OK</d:status></d:propstat></d:response>
+ <d:response><d:href>/dav/calendars/me/inbox/</d:href><d:propstat><d:prop><d:resourcetype><d:collection/><cal:schedule-inbox/></d:resourcetype></d:prop><d:status>HTTP/1.1 200 OK</d:status></d:propstat></d:response>
+</d:multistatus>`)
+		case r.Method == http.MethodGet && r.URL.Path == "/dav/calendars/me/gewicht/" && r.URL.RawQuery == "export":
+			io.WriteString(w, ics)
+		case r.Method == http.MethodGet && r.URL.Path == "/dav/calendars/me/broken/":
+			io.WriteString(w, "<html>login</html>")
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer srv.Close()
+
+	// An existing file must survive a broken download.
+	if err := os.WriteFile(filepath.Join(dir, "Broken_Name.ics"), []byte("old"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	results, err := syncCalendars(calendarSettings{CaldavURL: srv.URL + "/dav/calendars/me", CaldavUser: "me", CaldavPass: "secret"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(results) != 2 || results["Gewicht"].Error != "" || results["Broken_Name"].Error == "" {
+		t.Fatalf("results = %+v", results)
+	}
+	if got, _ := os.ReadFile(filepath.Join(dir, "Gewicht.ics")); string(got) != ics {
+		t.Fatalf("Gewicht.ics = %q", got)
+	}
+	if got, _ := os.ReadFile(filepath.Join(dir, "Broken_Name.ics")); string(got) != "old" {
+		t.Fatalf("broken download replaced the file: %q", got)
+	}
+
+	if _, err := syncCalendars(calendarSettings{CaldavURL: srv.URL + "/dav/calendars/me/", CaldavUser: "me", CaldavPass: "wrong"}); err == nil || !strings.Contains(err.Error(), "authentication") {
+		t.Fatalf("wrong password: err = %v", err)
+	}
+}
+
+func TestHasDotSegment(t *testing.T) {
+	for p, want := range map[string]bool{
+		"/Calendars/.page-settings": true,
+		"/.auth-key":                true,
+		"/a/.hidden/b.txt":          true,
+		"/Calendars/Personal.ics":   false,
+		"/a/b.c/":                   false,
+		"/a/../.auth-key":           true,
+		"/":                         false,
+	} {
+		if got := hasDotSegment(p); got != want {
+			t.Errorf("hasDotSegment(%q) = %v, want %v", p, got, want)
+		}
+	}
+}

calendarpage.go

@@ -0,0 +1,116 @@
+package main
+
+import (
+	"bytes"
+	"html/template"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func init() {
+	pageTypeHandlers = append(pageTypeHandlers, &calendarsHandler{})
+}
+
+// calendarsHandler renders folders whose .page-settings declares
+// type = calendars: the maintenance table and the sync status. Markdown
+// content and the listing stay visible, as in the fitness folder.
+type calendarsHandler struct{}
+
+func (c *calendarsHandler) redirect(root, fsPath, urlPath string, r *http.Request) (string, bool) {
+	return "", false
+}
+
+func (c *calendarsHandler) handle(root, fsPath, urlPath string, r *http.Request) *specialPage {
+	s := readPageSettings(fsPath)
+	if s == nil || s.Type != "calendars" {
+		return nil
+	}
+	return &specialPage{Content: renderCalendarsPage(fsPath), SuppressTOC: true}
+}
+
+type calFileRow struct {
+	Name    string
+	Roles   string
+	Events  string
+	Updated string // file modification time
+	Error   string // last sync or parse error
+}
+
+type calPageData struct {
+	HasMaintenance bool
+	Maintenance    []maintSeriesRow
+	Calendars      []calFileRow
+	// Sync is only shown for the configured calendars folder.
+	IsSyncDir   bool
+	SyncEnabled bool
+	LastRun     string
+	LastError   string
+}
+
+var calPageTmpl = template.Must(template.ParseFS(assets, "assets/calendar/page.html"))
+
+func renderCalendarsPage(dir string) template.HTML {
+	s := readCalendarSettings(dir)
+	data := calPageData{
+		HasMaintenance: len(s.Maintenance) > 0,
+		Maintenance:    maintenanceSeries(dir, s.Maintenance, time.Now()),
+		IsSyncDir:      calendarsDir != "" && dir == calendarsDir,
+		SyncEnabled:    s.CaldavURL != "",
+	}
+
+	var results map[string]calSyncResult
+	if data.IsSyncDir {
+		var lastRun time.Time
+		lastRun, data.LastError, results = calSyncSnapshot()
+		if !lastRun.IsZero() {
+			data.LastRun = lastRun.Format("2006-01-02 15:04")
+		}
+	}
+
+	roles := map[string][]string{}
+	for role, names := range map[string][]string{"diary": s.Diary, "weight": s.Weight, "maintenance": s.Maintenance} {
+		for _, n := range names {
+			roles[n] = append(roles[n], role)
+		}
+	}
+	entries, _ := os.ReadDir(dir)
+	for _, e := range entries {
+		name := e.Name()
+		if e.IsDir() || strings.HasPrefix(name, ".") || !strings.EqualFold(filepath.Ext(name), ".ics") {
+			continue
+		}
+		name = strings.TrimSuffix(name, filepath.Ext(name))
+		sort.Strings(roles[name])
+		row := calFileRow{Name: name, Roles: strings.Join(roles[name], ", "), Error: results[name].Error}
+		if info, err := e.Info(); err == nil {
+			row.Updated = info.ModTime().Format("2006-01-02 15:04")
+		}
+		if f := loadCalendar(filepath.Join(dir, e.Name())); f != nil {
+			row.Events = strconv.Itoa(f.events)
+		} else if row.Error == "" {
+			row.Error = "cannot parse file"
+		}
+		data.Calendars = append(data.Calendars, row)
+		delete(results, name)
+	}
+	// Calendars whose download failed before a file ever existed.
+	for name, r := range results {
+		if r.Error != "" {
+			data.Calendars = append(data.Calendars, calFileRow{Name: name, Error: r.Error})
+		}
+	}
+	sort.SliceStable(data.Calendars, func(i, j int) bool { return data.Calendars[i].Name < data.Calendars[j].Name })
+
+	var buf bytes.Buffer
+	if err := calPageTmpl.Execute(&buf, data); err != nil {
+		log.Printf("calendars page template: %v", err)
+		return ""
+	}
+	return template.HTML(buf.String())
+}

calsync.go

@@ -0,0 +1,296 @@
+package main
+
+import (
+	"bytes"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+	"strings"
+	"sync"
+	"time"
+)
+
+// The calendar sync mirrors every calendar of a CalDAV calendar home (e.g.
+// Nextcloud's /remote.php/dav/calendars/<user>/) into calendarsDir as
+// <display name>.ics. It runs in the background only: page renders read the
+// local files and never touch the network. A failed run leaves the previous
+// files in place.
+
+// calSyncMaxBody bounds a single calendar download.
+const calSyncMaxBody = 64 << 20
+
+var calSyncClient = &http.Client{Timeout: 60 * time.Second}
+
+// calSyncResult is the outcome of the last run for one calendar.
+type calSyncResult struct {
+	Updated time.Time // last successful download
+	Error   string
+}
+
+var calSync struct {
+	run sync.Mutex // serializes runs
+
+	mu        sync.Mutex // guards the fields below
+	lastRun   time.Time
+	lastError string // config/discovery error of the last run
+	results   map[string]calSyncResult
+}
+
+// startCalendarSync checks the settings once a minute and syncs when the
+// interval since the last run has passed. The first check happens right
+// away. Settings are read every time, so enabling the sync or changing the
+// interval needs no restart.
+func startCalendarSync() {
+	go func() {
+		for {
+			s := readCalendarSettings(calendarsDir)
+			if s.CaldavURL != "" {
+				calSync.mu.Lock()
+				last := calSync.lastRun
+				calSync.mu.Unlock()
+				if last.IsZero() || (s.SyncInterval > 0 && time.Since(last) >= s.SyncInterval) {
+					runCalendarSync()
+				}
+			}
+			time.Sleep(time.Minute)
+		}
+	}()
+}
+
+// runCalendarSync performs one sync run and records the outcome.
+func runCalendarSync() {
+	calSync.run.Lock()
+	defer calSync.run.Unlock()
+
+	results, err := syncCalendars(readCalendarSettings(calendarsDir))
+
+	calSync.mu.Lock()
+	defer calSync.mu.Unlock()
+	calSync.lastRun = time.Now()
+	calSync.lastError = ""
+	if err != nil {
+		calSync.lastError = err.Error()
+		log.Printf("calendar sync: %v", err)
+	}
+	if calSync.results == nil {
+		calSync.results = map[string]calSyncResult{}
+	}
+	for name, r := range results {
+		prev := calSync.results[name]
+		if r.Updated.IsZero() {
+			r.Updated = prev.Updated
+		}
+		calSync.results[name] = r
+		if r.Error != "" {
+			log.Printf("calendar sync %s: %s", name, r.Error)
+		}
+	}
+}
+
+// calSyncSnapshot returns a copy of the sync status for display.
+func calSyncSnapshot() (lastRun time.Time, lastError string, results map[string]calSyncResult) {
+	calSync.mu.Lock()
+	defer calSync.mu.Unlock()
+	results = make(map[string]calSyncResult, len(calSync.results))
+	for k, v := range calSync.results {
+		results[k] = v
+	}
+	return calSync.lastRun, calSync.lastError, results
+}
+
+// handleCalendarSync runs a sync now (POST ?calsync on the calendars page)
+// and returns to the page.
+func (h *handler) handleCalendarSync(w http.ResponseWriter, r *http.Request, urlPath, fsPath string) {
+	if calendarsDir == "" || fsPath != calendarsDir {
+		http.Error(w, "not the calendars folder", http.StatusBadRequest)
+		return
+	}
+	if readCalendarSettings(calendarsDir).CaldavURL == "" {
+		http.Error(w, "sync is not configured (caldav-url)", http.StatusBadRequest)
+		return
+	}
+	runCalendarSync()
+	http.Redirect(w, r, urlPath, http.StatusSeeOther)
+}
+
+// syncCalendars downloads every calendar of the calendar home. The returned
+// map has one entry per calendar that was attempted; err is set when nothing
+// could be attempted (bad settings, discovery failed).
+func syncCalendars(s calendarSettings) (map[string]calSyncResult, error) {
+	home, err := url.Parse(s.CaldavURL)
+	if err != nil || (home.Scheme != "http" && home.Scheme != "https") {
+		return nil, fmt.Errorf("invalid caldav-url %q", s.CaldavURL)
+	}
+	if !strings.HasSuffix(home.Path, "/") {
+		home.Path += "/"
+	}
+	cals, err := davDiscoverCalendars(home, s)
+	if err != nil {
+		return nil, err
+	}
+
+	results := map[string]calSyncResult{}
+	used := map[string]bool{}
+	for _, c := range cals {
+		name := calendarFileName(c.name, c.href)
+		if used[strings.ToLower(name)] {
+			name += " (" + path.Base(strings.TrimSuffix(c.href, "/")) + ")"
+		}
+		used[strings.ToLower(name)] = true
+
+		if err := syncOneCalendar(home, c.href, name, s); err != nil {
+			results[name] = calSyncResult{Error: err.Error()}
+			continue
+		}
+		results[name] = calSyncResult{Updated: time.Now()}
+	}
+	return results, nil
+}
+
+// syncOneCalendar downloads one calendar via Nextcloud's ?export and writes
+// it when the content changed. Invalid downloads (HTML error pages, broken
+// iCalendar) never replace the existing file.
+func syncOneCalendar(home *url.URL, href, name string, s calendarSettings) error {
+	u, err := home.Parse(href)
+	if err != nil {
+		return err
+	}
+	u.RawQuery = "export"
+	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
+	if err != nil {
+		return err
+	}
+	req.SetBasicAuth(s.CaldavUser, s.CaldavPass)
+	req.Header.Set("Accept", "text/calendar")
+	resp, err := calSyncClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("download: %s", resp.Status)
+	}
+	data, err := io.ReadAll(io.LimitReader(resp.Body, calSyncMaxBody+1))
+	if err != nil {
+		return err
+	}
+	if len(data) > calSyncMaxBody {
+		return errors.New("download: calendar larger than 64 MB")
+	}
+	if _, err := parseCalendar(name+".ics", data); err != nil {
+		return fmt.Errorf("invalid calendar data: %v", err)
+	}
+
+	p := calendarPath(calendarsDir, name)
+	if p == "" {
+		return fmt.Errorf("unusable file name %q", name)
+	}
+	if old, err := os.ReadFile(p); err == nil && bytes.Equal(old, data) {
+		return nil
+	}
+	if err := os.MkdirAll(calendarsDir, 0755); err != nil {
+		return err
+	}
+	return writeFileAtomic(p, data, 0644)
+}
+
+// calendarFileName turns a display name into a safe file basename. Falls back
+// to the last segment of the calendar's href.
+func calendarFileName(display, href string) string {
+	clean := strings.Map(func(r rune) rune {
+		if r < 0x20 || strings.ContainsRune(`/\:*?"<>|`, r) {
+			return '_'
+		}
+		return r
+	}, display)
+	clean = strings.TrimLeft(strings.TrimSpace(clean), ".")
+	if clean == "" {
+		clean = strings.TrimLeft(path.Base(strings.TrimSuffix(href, "/")), ".")
+	}
+	if clean == "" {
+		clean = "calendar"
+	}
+	return clean
+}
+
+// === Discovery ===
+
+type davCalendar struct {
+	href string
+	name string
+}
+
+const davPropfindBody = `<?xml version="1.0" encoding="utf-8"?>
+<d:propfind xmlns:d="DAV:"><d:prop><d:displayname/><d:resourcetype/></d:prop></d:propfind>`
+
+type davMultistatus struct {
+	Responses []struct {
+		Href      string `xml:"DAV: href"`
+		Propstats []struct {
+			Status string `xml:"DAV: status"`
+			Prop   struct {
+				DisplayName  string `xml:"DAV: displayname"`
+				ResourceType struct {
+					Types []struct {
+						XMLName xml.Name
+					} `xml:",any"`
+				} `xml:"DAV: resourcetype"`
+			} `xml:"DAV: prop"`
+		} `xml:"DAV: propstat"`
+	} `xml:"DAV: response"`
+}
+
+// davDiscoverCalendars lists the calendar collections directly below home
+// with one PROPFIND (Depth 1).
+func davDiscoverCalendars(home *url.URL, s calendarSettings) ([]davCalendar, error) {
+	req, err := http.NewRequest("PROPFIND", home.String(), strings.NewReader(davPropfindBody))
+	if err != nil {
+		return nil, err
+	}
+	req.SetBasicAuth(s.CaldavUser, s.CaldavPass)
+	req.Header.Set("Depth", "1")
+	req.Header.Set("Content-Type", "application/xml; charset=utf-8")
+	resp, err := calSyncClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("discovery: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode == http.StatusUnauthorized {
+		return nil, errors.New("discovery: authentication failed (check caldav-user / caldav-pass)")
+	}
+	if resp.StatusCode != http.StatusMultiStatus {
+		return nil, fmt.Errorf("discovery: %s", resp.Status)
+	}
+	var ms davMultistatus
+	if err := xml.NewDecoder(io.LimitReader(resp.Body, calSyncMaxBody)).Decode(&ms); err != nil {
+		return nil, fmt.Errorf("discovery: %v", err)
+	}
+
+	var out []davCalendar
+	for _, r := range ms.Responses {
+		for _, ps := range r.Propstats {
+			if !strings.Contains(ps.Status, " 200 ") {
+				continue
+			}
+			isCalendar := false
+			for _, t := range ps.Prop.ResourceType.Types {
+				if t.XMLName.Space == "urn:ietf:params:xml:ns:caldav" && t.XMLName.Local == "calendar" {
+					isCalendar = true
+				}
+			}
+			if isCalendar {
+				out = append(out, davCalendar{href: r.Href, name: strings.TrimSpace(ps.Prop.DisplayName)})
+			}
+		}
+	}
+	if len(out) == 0 {
+		return nil, errors.New("discovery: no calendars found at caldav-url")
+	}
+	return out, nil
+}

diary.go

@@ -533,6 +533,8 @@ type diarySection struct {
 	EditURL string        // year-file section edit URL ("" = no edit button)
 	Body    template.HTML // rendered markdown body (excludes the heading line)
 	Photos  []diaryPhoto
+	Events  string // day's calendar events, comma-separated (level 3 only)
+	Weight  string // day's weight from the weight calendar (level 3 only)
 }
 
 type diaryContentData struct {
@@ -623,6 +625,7 @@ func renderDiaryYear(yearFS, yearURL string) template.HTML {
 
 	out := buildFileSections(sections, photos, yearURL)
 	out = appendVirtualEntries(out, sections, photos, year, yearURL)
+	attachCalendarLines(out, year)
 	return renderDiaryContent(out)
 }
 
@@ -746,6 +749,28 @@ func appendVirtualEntries(existing []diarySection, sections [][]byte, photos []d
 	return out
 }
 
+// attachCalendarLines fills the events and weight lines of every day section
+// (real or virtual) from the calendars' diary and weight roles.
+func attachCalendarLines(sections []diarySection, year int) {
+	lines := calendarDayLines(
+		time.Date(year, time.January, 1, 0, 0, 0, 0, time.Local),
+		time.Date(year+1, time.January, 1, 0, 0, 0, 0, time.Local))
+	if len(lines) == 0 {
+		return
+	}
+	for i := range sections {
+		s := &sections[i]
+		if s.Level != 3 {
+			continue
+		}
+		if _, _, _, ok := parseISODate(s.ID); !ok {
+			continue
+		}
+		l := lines[s.ID[:10]]
+		s.Events, s.Weight = l.Events, l.Weight
+	}
+}
+
 // isRealDateSection reports whether a rendered diarySection is one of the
 // date-headed slots (`## YYYY-MM` or `### YYYY-MM-DD`) the virtual-entry
 // interleave sorts against.

go.mod

@@ -2,4 +2,8 @@ module datascape
 
 go 1.26.1
 
-require github.com/yuin/goldmark v1.8.2
+require (
+	github.com/emersion/go-ical v0.0.0-20250609112844-439c63cef608
+	github.com/teambition/rrule-go v1.8.2
+	github.com/yuin/goldmark v1.8.2
+)

go.sum

@@ -1,2 +1,6 @@
+github.com/emersion/go-ical v0.0.0-20250609112844-439c63cef608 h1:5XWaET4YAcppq3l1/Yh2ay5VmQjUdq6qhJuucdGbmOY=
+github.com/emersion/go-ical v0.0.0-20250609112844-439c63cef608/go.mod h1:BEksegNspIkjCQfmzWgsgbu6KdeJ/4LwUZs7DMBzjzw=
+github.com/teambition/rrule-go v1.8.2 h1:lIjpjvWTj9fFUZCmuoVDrKVOtdiyzbzc93qTmRVe/J8=
+github.com/teambition/rrule-go v1.8.2/go.mod h1:Ieq5AbrKGciP1V//Wq8ktsTXwSwJHDD5mD/wLBGl3p4=
 github.com/yuin/goldmark v1.8.2 h1:kEGpgqJXdgbkhcOgBxkC0X0PmoPG1ZyoZ117rDVp4zE=
 github.com/yuin/goldmark v1.8.2/go.mod h1:ip/1k0VRfGynBgxOz0yCqHrbZXhcjxyuS66Brc7iBKg=

main.go

@@ -17,6 +17,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
+	_ "time/tzdata" // calendar TZIDs must resolve even without system zoneinfo
 )
 
 //go:embed assets
@@ -38,10 +39,13 @@ func hashAsset(name string) string {
 }
 
 // tmplFuncs is shared by every layout-based template: the edit template appends
-// editorBundleVersion to its CodeMirror <script> src to cache-bust the bundle.
+// editorBundleVersion to its CodeMirror <script> src to cache-bust the bundle;
+// the layout header renders the maintenance widget.
 var tmplFuncs = template.FuncMap{
 	"editorBundleVersion": func() string { return editorBundleVersion },
 	"fileIcon":            fileIcon,
+	"icon":                readIcon,
+	"maintenanceWidget":   maintenanceWidget,
 }
 
 var (
@@ -88,8 +92,18 @@ func main() {
 	user := flag.String("user", "", "basic auth username (empty = no auth)")
 	pass := flag.String("pass", "", "basic auth password")
 	reindexInterval := flag.Duration("reindex-interval", 30*time.Minute, "periodic search index rebuild interval (0 disables)")
+	calendars := flag.String("calendars", "Calendars", "calendars folder, relative to -dir (empty disables)")
+	tz := flag.String("tz", "", "time zone for calendars and the diary, e.g. Europe/Berlin (default: system)")
 	flag.Parse()
 
+	if *tz != "" {
+		loc, err := time.LoadLocation(*tz)
+		if err != nil {
+			log.Fatalf("-tz: %v", err)
+		}
+		time.Local = loc
+	}
+
 	root, err := filepath.Abs(*wikiDir)
 	if err != nil {
 		log.Fatal(err)
@@ -108,6 +122,15 @@ func main() {
 
 	initMarkdown()
 
+	if *calendars != "" {
+		calendarsDir = filepath.Join(root, filepath.FromSlash(*calendars))
+		rel, err := filepath.Rel(root, calendarsDir)
+		if err != nil || rel == "." || strings.HasPrefix(rel, "..") {
+			log.Fatalf("-calendars must be a folder inside -dir")
+		}
+		calendarsURL = "/" + filepath.ToSlash(rel) + "/"
+	}
+
 	authKey, err := loadOrCreateAuthKey(root)
 	if err != nil {
 		log.Fatal(err)
@@ -158,6 +181,10 @@ func main() {
 		}(*reindexInterval)
 	}
 
+	if calendarsDir != "" {
+		startCalendarSync()
+	}
+
 	log.Printf("datascape listening on %s, wiki at %s", *addr, root)
 	log.Fatal(http.ListenAndServe(*addr, nil))
 }
@@ -188,6 +215,14 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Dotfiles are never served: .page-settings can hold the CalDAV
+	// password and .auth-key signs sessions. Nothing links to them (listing,
+	// tree and search hide them already).
+	if hasDotSegment(r.URL.Path) {
+		http.NotFound(w, r)
+		return
+	}
+
 	if strings.HasPrefix(r.URL.Path, thumbURLPrefix+"/") {
 		h.handleThumb(w, r)
 		return
@@ -255,6 +290,17 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// hasDotSegment reports whether any segment of the cleaned URL path starts
+// with a dot.
+func hasDotSegment(p string) bool {
+	for _, seg := range strings.Split(path.Clean("/"+p), "/") {
+		if strings.HasPrefix(seg, ".") {
+			return true
+		}
+	}
+	return false
+}
+
 // slashedURL returns u's path with a trailing slash appended and the query
 // string intact — the canonical page form that relative destinations resolve
 // against.
@@ -414,6 +460,10 @@ func (h *handler) handlePost(w http.ResponseWriter, r *http.Request, urlPath, fs
 		h.handleSettings(w, r, urlPath, fsPath)
 		return
 	}
+	if query.Has("calsync") {
+		h.handleCalendarSync(w, r, urlPath, fsPath)
+		return
+	}
 
 	if err := r.ParseForm(); err != nil {
 		http.Error(w, "bad request", http.StatusBadRequest)
@@ -525,12 +575,28 @@ func (h *handler) handlePost(w http.ResponseWriter, r *http.Request, urlPath, fs
 // Returns nil if the file does not exist.
 // Format: one "key = value" pair per line; lines starting with # are comments.
 func readPageSettings(dir string) *pageSettings {
+	kv := readSettingsFile(dir)
+	if kv == nil {
+		return nil
+	}
+	// Unknown or missing values fall back to the defaults.
+	return &pageSettings{
+		Type:  kv["type"],
+		View:  validateView(kv["view"]),
+		Sort:  validateSort(kv["sort"]),
+		Order: validateOrder(kv["order"]),
+	}
+}
+
+// readSettingsFile returns every key of dir's .page-settings (last one wins),
+// or nil if the file does not exist. Other features (e.g. the calendars
+// folder) keep their own keys in the same file.
+func readSettingsFile(dir string) map[string]string {
 	data, err := os.ReadFile(filepath.Join(dir, ".page-settings"))
 	if err != nil {
 		return nil
 	}
-	// Defaults; overridden only by valid values present in the file.
-	s := &pageSettings{View: viewList, Sort: sortName, Order: orderAsc}
+	kv := map[string]string{}
 	for _, line := range strings.Split(string(data), "\n") {
 		line = strings.TrimSpace(line)
 		if line == "" || strings.HasPrefix(line, "#") {
@@ -540,17 +606,7 @@ func readPageSettings(dir string) *pageSettings {
 		if len(parts) != 2 {
 			continue
 		}
-		value := strings.TrimSpace(parts[1])
-		switch strings.TrimSpace(parts[0]) {
-		case "type":
-			s.Type = value
-		case "view":
-			s.View = validateView(value)
-		case "sort":
-			s.Sort = validateSort(value)
-		case "order":
-			s.Order = validateOrder(value)
-		}
+		kv[strings.TrimSpace(parts[0])] = strings.TrimSpace(parts[1])
 	}
-	return s
+	return kv
 }

maintenance.go

@@ -0,0 +1,144 @@
+package main
+
+import (
+	"bytes"
+	"html/template"
+	"log"
+	"sort"
+	"time"
+)
+
+// calendarsURL is the page URL of calendarsDir ("/Calendars/").
+var calendarsURL string
+
+// maintenanceHorizon is how many days after today the header widget lists.
+const maintenanceHorizon = 7
+
+type maintItem struct {
+	When    string // "03:00" today; "Sa 27.09." or "Sa 27.09. 03:00" later
+	Summary string
+}
+
+type maintWidgetData struct {
+	Count    int // occurrences today (the badge)
+	Today    []maintItem
+	Upcoming []maintItem
+	PageURL  string
+}
+
+var maintWidgetTmpl = template.Must(template.New("widget.html").
+	Funcs(template.FuncMap{"icon": readIcon}).
+	ParseFS(assets, "assets/calendar/widget.html"))
+
+// maintenanceWidget renders the header chip and its dropdown. It is a
+// template func so layout.html can call it without every page's data struct
+// carrying it. Empty when no maintenance calendar is configured.
+func maintenanceWidget() template.HTML {
+	if calendarsDir == "" {
+		return ""
+	}
+	names := readCalendarSettings(calendarsDir).Maintenance
+	if len(names) == 0 {
+		return ""
+	}
+	now := time.Now()
+	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, time.Local)
+	tomorrow := today.AddDate(0, 0, 1)
+
+	data := maintWidgetData{PageURL: calendarsURL}
+	for _, ev := range calendarOccurrences(calendarsDir, names, today, today.AddDate(0, 0, maintenanceHorizon+1)) {
+		// Anything that started before tomorrow is due today, including
+		// multi-day events still running.
+		if ev.Start.Before(tomorrow) {
+			item := maintItem{Summary: ev.Summary}
+			if !ev.AllDay && !ev.Start.Before(today) {
+				item.When = ev.Start.Format("15:04")
+			}
+			data.Today = append(data.Today, item)
+			continue
+		}
+		when := calDayLabel(ev.Start)
+		if !ev.AllDay {
+			when += " " + ev.Start.Format("15:04")
+		}
+		data.Upcoming = append(data.Upcoming, maintItem{When: when, Summary: ev.Summary})
+	}
+	data.Count = len(data.Today)
+
+	var buf bytes.Buffer
+	if err := maintWidgetTmpl.Execute(&buf, data); err != nil {
+		log.Printf("maintenance widget template: %v", err)
+		return ""
+	}
+	return template.HTML(buf.String())
+}
+
+// maintSeriesRow is one task in the calendars page's maintenance table.
+type maintSeriesRow struct {
+	Summary string
+	Rule    string
+	Last    string // most recent occurrence before today
+	Next    string // first occurrence today or later
+	next    time.Time
+}
+
+// maintenanceWindow bounds the table's occurrence search, in days each way
+// from today. A year covers yearly tasks.
+const maintenanceWindow = 366
+
+// maintenanceSeries lists every task of the named calendars in dir: one row
+// per recurring series with its last and next date, plus upcoming single
+// events. Sorted by next date; series without a next date come last.
+func maintenanceSeries(dir string, names []string, now time.Time) []maintSeriesRow {
+	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, time.Local)
+	evs := calendarOccurrences(dir, names, today.AddDate(0, 0, -maintenanceWindow), today.AddDate(0, 0, maintenanceWindow))
+
+	type key struct{ calendar, uid string }
+	rows := map[key]*maintSeriesRow{}
+	var order []*maintSeriesRow
+	for _, ev := range evs {
+		if ev.Series == nil {
+			if ev.Start.Before(today) {
+				continue
+			}
+			order = append(order, &maintSeriesRow{
+				Summary: ev.Summary,
+				Rule:    "once",
+				Next:    calDayLabel(ev.Start),
+				next:    ev.Start,
+			})
+			continue
+		}
+		k := key{ev.Calendar, ev.Series.UID}
+		row := rows[k]
+		if row == nil {
+			row = &maintSeriesRow{Summary: ev.Series.Summary, Rule: ev.Series.Rule}
+			rows[k] = row
+			order = append(order, row)
+		}
+		// Occurrences arrive sorted by start: keep overwriting Last, take
+		// the first one from today on as Next.
+		if ev.Start.Before(today) {
+			row.Last = calDayLabel(ev.Start)
+		} else if row.next.IsZero() {
+			row.next = ev.Start
+			row.Next = calDayLabel(ev.Start)
+		}
+	}
+
+	out := make([]maintSeriesRow, 0, len(order))
+	for _, r := range order {
+		out = append(out, *r)
+	}
+	sort.SliceStable(out, func(i, j int) bool {
+		a, b := out[i].next, out[j].next
+		if a.IsZero() != b.IsZero() {
+			return b.IsZero()
+		}
+		if !a.Equal(b) {
+			return a.Before(b)
+		}
+		return out[i].Summary < out[j].Summary
+	})
+	return out
+}