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Caldav sync for Emacs orgmode

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README.md

org-caldav

Caldav sync for Emacs Orgmode

Tested CalDAV servers: Owncloud

Google Calendar works on old, deprecated endpoint only. New endpoint requires OAuth2 authentication. See issue #28 on why that's a problem.

Also reported to be working: SOGo.

IMPORTANT: Before using this code, please make sure you have backups of your precious Org files. Also, I strongly suggest to create a new, empty calendar on your server for using this package.

ALSO IMPORTANT: When using this package, possibly all Org entries will get an UID property (see doc-string of org-icalendar-store-UID for further details). If you don't want this, then do not use this package; there is just no way around that. It is the only reliable way to uniquely identify Org entries.

This package depends on the url-dav package, which unfortunately is broken in Emacs <=24.2. If you don't want to upgrade Emacs, you can get a working version here:

http://randomsample.de/url-dav.el

Now load this file before using org-caldav. However, since those manual overrides of core libraries tend to be forgotten and might bite you later on, I'd rather recommend upgrading to a newer Emacs version.

IN A NUTSHELL

  • Create a new calendar; the name does not matter.

  • Set org-caldav-url to the base address of your CalDAV server:

  • Set org-caldav-calendar-id to the calendar-id of your new calendar:

    • OwnCloud: Simply the name of the calendar.
    • Google: Click on 'calendar settings' and the id will be shown next to "Calendar Address". It is of the form ID@group.calendar.google.com. Do not omit the domain!
  • Set org-caldav-inbox to an org filename where new entries from the calendar should be stored. Just to be safe, I suggest using an empty, dedicated Org file for that.

  • Set org-caldav-files to the list of org files you would like to sync. The above org-caldav-inbox will be automatically added, so you don't have to add it here.

  • It is usually a good idea to manually set org-icalendar-timezone to the timezone of your remote calendar. It should be a simple string like "Europe/Berlin". If that doesn't work and your events are shifted by a few hours, try the setting "UTC" (the SOGo calendar server seems to need this).

You can also take a look at the other org-icalendar variables, since org-caldav uses this package to export your entries.

Call org-caldav-sync to start the sync. The URL package will ask you for username/password for accessing the calendar. (See below on how to store that password in an authinfo file.)

The first sync can easily take several minutes, depending on the number of calendar items. Especially Google's CalDAV interface is pretty slow. If you have to abort the initial sync for some reason, just start org-caldav-sync again in the same Emacs session and you should get asked if you'd like to resume.

The same goes for sync errors you might get. Especially when using Google Calendar, it is not unusual to get stuff like '409' errors during the initial sync. Only Google knows why. Just run org-caldav-sync again until all events are uploaded.

DETAILS

Compared to earlier versions of this package from 2012, it now does proper two-way syncing, that means it does not matter where and how you change an entry. You can also move Org entries freely from one file to another, as long as they are all listed in org-caldav-files. The org-icalendar package will put a unique ID on each entry with an active timestamp, so that org-caldav can find it. It will also sync deletions, but more on that later.

Org and the iCalendar format

An Org entry can store much more information than an iCalendar entry, so there is no one-to-one correspondence between the two formats which makes syncing a bit difficult.

  • Org to iCalendar

This package uses the org-icalendar package to do the export to the iCalendar format (.ics files). By default, it uses the title of the Org entry as SUMMARY and puts the entry's body into DESCRIPTION, snipping stuff like properties and timestamps (you can override that with properties of the same name, but IMO it makes stuff just more complicated). The variable org-icalendar-include-body (100 by default) denotes how many characters from the body should be included as DESCRIPTION.

  • iCalendar to Org

If you create a new iCalendar entry in your calendar, you'll get an Org entry with SUMMARY as heading, DESCRIPTION as body and the timestamp. However, if you change an existing entry in the calendar, things get more complicated and the variable org-caldav-sync-changes-to-org comes into play. Its default is the symbol "title-and-timestamp", which means that only the entry's heading is synced (with SUMMARY) and the timestamp gets updated, but not the entry's body with DESCRIPTION. The simple reason is that you might loose data, since DESCRIPTION is rather limited in what it can store. Still, you can set the variable to the symbol "all", which will completely replace an existing Org entry with the entry that gets generated from the calendar's event. You can also limit syncing to heading and/or timestamp only.

To be extra safe, org-caldav will by default backup entries it changes. See the variable org-caldav-backup-file for details.

  • Org sexp entries

A special case are sexp entries like

%%(diary-anniversary  2 2 1969) Foo's birthday

* Regular meeting
  <%%(diary-float t 4 2)>

As you can see, they can appear in two different ways: plain by themselves, or inside an Org entry. If they are inside an Org entry, there's a good chance they will be exported (see below) and have an ID property, so they can be found by org-caldav. We can sync the title, but syncing the timestamp with the s-expression is just infeasible, so this will generate a sync error (which are not critical; you'll just see them at the end of the sync, just so that you're aware that some stuff wasn't synced properly).

However, sexp-entries are insanely flexible, and there are limits as to what the icalendar exporter will handle. For example, this here

** Regular event
   <%%(memq (calendar-day-of-week date) '(1 3 5))>

will not be exported at all.

If the sexp entry is not inside an Org entry but stands by itself, they still will be exported, but they won't get an ID (since IDs are properties linked to Org entries). In practice, that means that you can delete and change them inside Org and this will be synced, but if you change them in the calendar, this will not get synced back. Org-caldav just cannot find those entires, so this will generate a one-time sync error instead (again: those are not critical, just FIY). If you don't want those entries to be exported at all, just set org-icalendar-include-sexps to nil.

Syncing deletions

If you delete entries in your Org files, the corresponding iCalendar entries will simply get deleted.

If you delete events in your calendar, you will by default get asked if you'd like to delete the corresponding Org event. You can change that behavior through org-caldav-delete-org-entries.

If you answer a deletion request with "no", the event should get re-synced to the calendar next time you call org-caldav-sync.

Conflict handling

Now that's an easy one: Org always wins. That means, if you change an entry in Org and in the calendar, the changes in the calendar will be lost. I might implement proper conflict handling some day, but don't hold your breath (patches are welcome, of course).

Storing authentication information in authinfo/netrc

If you don't want to enter your user/password every time, you can store it permanently in an authinfo file. In Emacs, the auth-source package takes care of that, but the syntax for https authentication is a bit peculiar. You have to use a line like the following

machine www.google.com:443 port https login username password secret

Note that you have to specify the port number in the URL and also specify 'https' for the port. This is not a bug. For more information, see (info "auth"), especially section "Help for users".

Since you are storing your password in a file it makes sense to encrypt it using GnuPG. While Emacs supports this, there's a subtle bug which makes this feature unusable for the URL package (see bug 11981). This was fixed in Emacs 24.2, so if you're using an older version, you'll have to upgrade if you want encrypted authinfo files for org-caldav.

Storage of sync information and sync from different computers

The current sync state is stored in a file org-caldav-SOMEID.el in the ~/.emacs.d directory. You can change the location through the variable org-caldav-save-directory. SOMEID directly depends on the calendar id (it's a snipped MD5).

If you sync your Org files across different machines and want to use org-caldav on all of them, don't forget to sync the org sync state, too. Probably your best bet is to set org-caldav-save-directory to the path you have your Org files in, so that it gets copied alongside with them.

Starting from scratch

If your sync state somehow gets broken, you can make a clean slate by doing

C-u M-x org-caldav-delete-everything

The function has to be called with a prefix so that you don't call it by accident. This will delete everything in the calendar along with the current sync state. You can then call org-caldav-sync afterwards and it will completely put all Org events into the now empty calendar. Needless to say, don't do that if you have new events in your calendar which are not synced yet...

Deleting many events can be slow, though; in that case, just delete the calendar and re-create it, delete the sync state file in ~/.emacs.d and restart Emacs.

Syncing with more than one calendar

This can be done by setting the variable org-caldav-calendars. It should be a list of plists (a 'plist' is simply a list with alternating :key's and values). Through these plists, you can override the global values of variables like org-caldav-calendar-id, and calling org-caldav-sync will go through these plists in order.

Example:

(setq org-caldav-calendars
  '((:calendar-id "work@whatever" :files ("~/org/work.org")
     :inbox "~/org/fromwork.org")
    (:calendar-id "stuff@mystuff"
     :files ("~/org/sports.org" "~/org/play.org")
     :inbox "~/org/fromstuff.org")) )

This means that you have two calendars with IDs "work@whatever" and "stuff@mystuff". Both will be accessed through the global value of org-caldav-url, since the key :url isn't specified. The calendar "work@whatever" will be synced with the file 'work.org' and inbox 'fromwork.org', while "stuff@mystuff" with 'sports.org' and 'play.org' and inbox 'fromstuff.org'. See the doc-string of org-caldav-calendars for more details on which keys you can use.

Additional stuff

See the doc-string of org-caldav-inbox if you want more flexibility in where new items should be put. Instead of simply providing a file, you can also choose an existing entry or headline.

Also, you can use org-caldav-select-tags to filter the tags that should be exported.

Timezone problems

Timezone handling is plain horrible, and it seems every CalDAV server does it slightly differently, also using non-standard headers like X-WR-TIMEZONE. If you see items being shifted by a few hours, make really really sure you have properly set org-icalendar-timezone, and that your calendar is configured to use the same one.

If it still does not work, you can try setting org-icalendar-timezone to the string "UTC". This will put all events using UTC times and the server should transpose the time to the timezone you have set in your calendar preferences. For some servers (like SOGo) this might work better than setting a "real" timezone.

Troubleshooting

By default, org-caldav will put all kinds of debug output into the buffer *org-caldav-debug*. Look there if you're getting sync errors or if something plain doesn't work. If you're using an authinfo file and authentication doesn't work, set auth-info-debug to t and look in the *Messages* buffer. When you report a bug, please try to post the relevant portion of the *org-caldav-debug* buffer since it might be helpful to see what's going wrong. If Emacs throws an error, do

M-x toggle-debug-on-error

and try to replicate the error to get a backtrace.

You can also turn on excessive debugging by setting the variable org-caldav-debug-level to 2. This will also output the contents of the events into the debug buffer. If you send such a buffer in a bug report, please make very sure you have removed personal information from those events.

Known Bugs

  • Recurring events created or changed on the calendar side cannot be synced (they will work fine as long as you manage them in Org, though).

  • Syncing is currently pretty slow since everything is done synchronously.

  • Pretty much everything besides SUMMARY, DESCRIPTION and time is ignored in iCalendar (like 'LOCATION', for instance).

How syncing happens (a.k.a. my little CalDAV rant)

(This is probably not interesting, so you can just stop reading.)

CalDAV is a mess.

First off, it is based on WebDAV, which has its own fair share of problems. The main design flaw of CalDAV however, is that UID and ressource name (the "filename", if you want) are two different things. I know that there are reasons for that (not everything has a UID, like timezones, and you can put several events in one ressource), but this is typical over-engineering to allow some marginal use cases pretty much no one needs. Another problem is that you have to do additional round-trips to get Etag and sequence number, which makes CalDAV pretty slow.

Org-caldav takes the easy route: it assumes that every ressource contains one event, and that UID and ressource name are identical. In fact, Google's CalDAV interface even enforces the latter. And while Owncloud does not enforce it, at least it just does it if you create items in its web interface.

However, the CalDAV standard does not demand this, so I guess there are servers out there with which org-caldav does not work. Patches welcome.

Now, all this would be bad enough if it weren't for the sloppy server implementations which make implementing a CalDAV client a living hell and led to several rewrites of the code. Especially Google, the 500 pound gorilla in the room, doesn't really care much for CalDAV. I guess they really like their own shiny REST-based calendar API better, and I can't blame them for that.

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