feat(android): back the calendars up as an iCalendar file

A Calendar section sends every calendar the person can edit, as a dated .ics,
into <folder>/<account>-calendar once a day when it changed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/docs/USERGUIDE.md b/docs/USERGUIDE.md
index e0c29da..1587160 100644
--- a/docs/USERGUIDE.md
+++ b/docs/USERGUIDE.md
@@ -385,7 +385,7 @@ that matters to you.
 ### Backing up your phone
 
 On the Android application, **Phone → Android Sync** in the side menu backs up
-your phone's photos, contacts and text messages to a group.
+your phone's photos, contacts, calendar and text messages to a group.
 
 Only your **personal profile** is backed up. If your phone has a work profile,
 nothing in it is sent, and MeshBay installed inside the work profile offers no
@@ -434,6 +434,17 @@ backup at all.
 - It runs on any connection, since a copy is small. **Back up now** sends one
   at once if your contacts changed since the last copy.
 
+#### Calendar
+
+- **Turn on** asks for access to your calendars, then sends a copy once a day
+  when they have changed.
+- It holds every calendar you can edit: your own, local ones and those of the
+  accounts on the phone. Calendars you only subscribe to (public holidays,
+  birthdays) are left out.
+- Each copy is an `.ics` file with the date in its name
+  (`calendar-2026-10-10-0900.ics`). Any calendar application can import it;
+  repeating events, their exceptions and reminders come along.
+
 #### Text messages
 
 - **Turn on** asks for access to your text messages. The first copy holds them