Google is changing the Location URL of their CalDAV Calendars

Google has decided to change the authentication mechanism for their CalDAV calendars to OAuth, which required some changes in Lightning to accommodate.

Due to these changes, the URL to access the calendar has also changed. The old endpoint will stop working after September 16th (today!). This affects only Google calendars using CalDAV protocol.

Calendars using the Provider for Google Calendar or iCal read-only access won’t be affected.

How do I know if I’m affected?

Open your calendar’s properties by right-clicking on calendar name and check if the location starts with If it does, you are using CalDAV and need to set up your calendar again with the new URL.

How do I set up the new calendar?

To use the new CalDAV Endpoint, you will need Lightning 2.6 and Thunderbird 24, which will be released tomorrow, September 17th. There will be a blog post on the release tomorrow, so please use the navigation to view the new post when its there to get the download links. Anyway, here are the steps:

  • Download Thunderbird 24 and install Lightning 2.6
  • Open the new calendar dialog (File → New → Calendar)
  • Add a new remote calendar (On the Network → CalDAV)
  • As a location enter the following, be sure to replace your email address:

More details on how to set up from Google can be found here. After setting up new calendar you can safely remove the old one from Lightning. This will only remove it from calendars list, your events will not be deleted from Google’s servers.

But I want it to work now!

In that case, you will have to use a beta version of Thunderbird and Lightning. You can get Thunderbird 24.0b3 here and the corresponding Lightning 2.6b2 here. Please use these versions only if you really can’t wait, once the release version is out there will be no support for beta versions.

One more thing…

Its a little unfortunate that Google is shutting down the API in coincidence with the release. I’m pretty sure a few people will blame Lightning’s new version for this (understandably, since that is the only thing they knowingly changed). This will mean we will get a few support requests covered as bad reviews, I already saw one today! If you found this blog post useful, please stop by and give us a few stars.

Update on addresses

If you created your Google account with an email address, you will need to use this email address in the URL, even if you’ve switched to now! Otherwise it will look like everything works, until you try to add/modify events. I will notify the Google folks so they can get this bug fixed on their end.

Update: Still not working? Here is why!

Unfortunately there are two more problems. First of all, you may be experiencing an instant failure, if you inspect the logs you might see an error 400. Aside from the location change, Google has also introduced support for webdav-sync. In theory this makes the synchronization process faster, but Google does not implement the fallback mechanism we rely on. We can probably fix this on our side though by updating to a newer version of the webdav-sync draft.

Next up is a bug on our side. When the OAuth token expires, there is an error refreshing the token. I will take care of fixing this for Lightning 2.6.1

But I really need it to work now!

Ok then, I have one option left for you. For the time being you could switch to the Provider for Google Calendar, an extension that uses the Google Calendar API to connect. You will have to set up the calendar a bit differently, using the new “Google Calendar” option in the new calendar wizard and the XML address as the location URL.

Thanks to Merike Sell for drafting this blog post


  1. Hi,
    I can not see the left part of the window where i was able to select a calendar.
    If I have to calendars how could i delete one now?
    Regards Markus

    • It probably got collapsed. I see its pretty much impossible to restore it using the mouse, thats definitely a bug. Please use the following workaround:

      Go to: Tools → Error Console
      Enter the following string and press enter:

  2. Cool that I don’t need to run the provider plugin – however it is too bad we still don’t have Task functionality.

    I’m using a windows 8 app called Metro Tasks – but having it in TB would be so much more awesome.

  3. For info: Google’s page about change in CALDAV URL.

  4. Hi, I did not succeed to access my GoogleCalendar by pasting the path given in this post (and given although by Google on their site linked in your post). I did the following to succeed:

    Sign in Google Calendar
    Settings > Settings -> Calendar Settings:
    Calendars: choose one > Calendar Address: Select Private Address “ical” -> paste this path in Lightning

    • This will likely cause the calendar to be readonly. If you want read-write access you need to chose the CalDAV option in the new calendar dialog.

  5. I expect to get a R/W access to my 3 google’s agendas

    I’m W7, thunderbird 24, ligthning 2.6, “fournisseur pour google agenda” 0.18

    It use to work ok when I was W7, thuderbird 17 with lighthning 1.9.1

    1. I deleted my 3 google agendas from lightning
    2. I updated thunderbird and lighthning
    3. I tried to re-create my agenda using “google agenda” and xml private URL
    4. I entered the password related to the googl agendas’owner and re-enter without ending.
    5. I then creted OK my 1st agenda through ICAL with following address as the doc said
    6. Impossible to create my 2 other google’s agenda. I received the warning “you’re already registered for this agenda in this location

    thnak you for helping

    • Please upgrade the Provider for Google Calendar to version 0.25

      • Oh my God!!! Thanks a lot for your explanations! My problema was the same related by gilles, but now everythings is OK!!!
        – Install the newest version of Linghtning e update or install Provider for Google Calendar 0.25, just it.
        – After thar it’ll be possible to add a Google Calendar, with authetication…


  6. Mike Kellenberger

    Can’t get this to work reliably. I have 3 calenders that I’m trying to connect via Google CALDAV V2. Sometimes it works, sometimes the calender gets disabled by itself and can’t be enabled again and most of the times I get the dreaded yellow warning sign. The messages in the error console dont’ help much in debugging the cause. At the moment, after deleting the calendars and their saved passwords and re-adding them I have 2 calendars which seem to be OK, but are showing NO calendar events whatsoever and one calendar which gets disabled as soon as I try to enable it.

  7. Jørgen Rasmussen

    I have changed to the new location url right after I updated to Thunderbird 24.0 and Lightning 2.6.
    Unfortunately I keep getting problems. After some time my Google calendar gets a warning sign: Calendar Google is momentarily not available. Here is what I can read in the error console:
    CalDAV: Status 401 checking ctag for calendar Google
    CalDAV: Error fetching item etags
    [JavaScript Warning: There has been an error reading data for calendar: Google. However, this error is believed to be minor, so the program will attempt to continue. Error code: DAV_REPORT_ERROR. There has been an error reading data for calendar: It has been disabled until it is safe to use it.
    When I try to switch the calendar back on, this is written in the error console: CalDAV: Status 401 on initial PROPFIND for calendar Google.
    Restarting Thunderbird makes it possible to turn it back on, but after a couple of hours the problem is back.
    Am I the only one having this problem?

    • Did you possibly have an address earlier? Try using that instead of

      • Jørgen Rasmussen

        Hi Philipp
        My email address has always been
        I have just tried with, but unfortunately with the same result.

    • I’m getting the exact same error messages…. so you are not alone…

    • Getting the same error, and then yet another one:
      [JavaScript Warning: “CalDAV: Error doing webdav sync: 400”]
      [JavaScript Warning: … Error code: DAV_REPORT_ERROR … ]
      [JavaScript Warning: … Error code: READ_FAILED …]
      [JavaScript Error: “CalCachedCalendar] replay action failed: null, uri=https://… result=2147500037, op=[xpconnect wrapped calIOperation]”]

      By the way, – it is very annoying that one cannot copy and paste errors from the logs! Is it 2013 or 1983?

      TB: v 24.0.1 Lightning 2.6 – both updated on October 14, 2013. Webdav is setup as described in the blog.

    • having the same EXACT error after a few hours. Still waiting for a fix to roll-out.


  8. I upgraded to TB 24 (from v17) and Lightning 2.6 (from v1.9.1). I no longer can access my Google calendar. It keeps asking me for my Login. The network location I have been using since I set it up well over a year ago is “{e-mail address}/public/basic” which is the XML format indicated for my calendar. I had no issue before this update. What do I have to do to regain access to my calendar.


    • Never mind. I updated Provider for Google Calendar to v0.25 and that fixed everything.

      • What did you do? I’ve reinstalled Lightning 2.6 and Provider 0.25, configured the private XML but I still cannot have Lightning working on Ubuntu 13.04.

      • Cheers for that JohnD – installed Provider 0.25 add on fixed it for me too!

  9. There seems to be a widespread issue with Lightning and the new V2 CalDav. See I suffer from this too. It makes CalDav almost a non-option on Thunderbird 24.0 + Lightning 2.6 which used to work so well before (TB 17.0.8 + previous version of GCal).

  10. I have Davical as local CalDAV server. After upgrading to Seamonkey 2.21 and Lightning 2.6b2 the following exception is thrown when opening the MailNews window:

    [Exception… “Component returned failure code: 0x80570015 (NS_ERROR_XPC_CI_RETURNED_FAILURE) [nsIJSCID.createInstance]” nsresult: “0x80570015 (NS_ERROR_XPC_CI_RETURNED_FAILURE)” location: “JS frame :: resource://calendar/modules/calUtils.jsm -> file:///C:/Users/hb/AppData/Roaming/Mozilla/SeaMonkey/Profiles//extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/calendar-js/calCalendarManager.js :: cmgr_createCalendar :: line 474” data: no]

  11. My toast e-mail and calendars are part of a Google account. I have updated Thunderbird and Lightning, and have switched to the new apidata calendar addresses. After I put my Toast e-mail address and password in, I get access to my Google calendars for a while. Then when I try to access the calendars after some minutes, I also get the 401 error message.

    If I delete the passwords and restart Thunderbird, I am asked to enter the passwords again. The calendars are once again available for some time.

  12. I’m having also troubles with lightning and google calendar… I have all the latest versions from thunderbird and lightning, but after i create new calendar with this link “” my TB freezes for long time…
    Eventually I get the calendar on TB but short after i get also that yellow sign :(

    Some help needed please.


  13. Previous to the exception above another one this thrown too:

    Fehler: NS_ERROR_FILE_NOT_FOUND: Component returned failure code: 0x80520012 (NS_ERROR_FILE_NOT_FOUND) [nsIXPCComponents_Utils.import]
    Quelldatei: resource://calendar/modules/OAuth2.jsm
    Zeile: 12

  14. In versions Lightning 2.7a2 and Seamonkey 2.22a2 this error is gone and connecting to a CalDAV server possible again.

  15. When I re-created the google calendar in latest TB/Lightning it opened google page to confirm access. I confirm and calendar works for some time. After some time (not sure, about 1 hour or so) calendar disconnects and shows warning sign. Not possible to reconnect. Delete/create it again gives access for some time again.
    There maybe a problem with refresh token in auth?

  16. Hello,

    I have updated my calender address to the new format

    I add a new calender to TB, CalDav, select my email address (as I need to be able to Accept meeting invitations), a popup window opens “Lightning. This app would like to Manage your Calenders”, I click Accept, click Finish.

    But my calender doesn’t load, TB only shows an ! in a yellow triangle.

    Any ideas???

  17. It would be very useful if Lightning allowed to EDIT the Location field.

    I access 14 Google CalDAV calendars, and the thought of having to re-create all of them is very disheartening.

    • I absolutely concur, not being able to edit this seems quite stone-age…

      • Philipp Kewisch

        From a user perspective I fully understand this. The way the current calendars are built its a bit tricky for the developer though, changing the URL could essentially change all cached properties of the calendar. This is especially true for caldav, where some of the retrieved sub-urls are cached.

        • So, all the users have to create new new calendars each time, instead of editing the existing ones? This is especially annoying in situations as the one happening now, – when there is a persistent error (with the newest version of both TB and Lightning), and so, one has to tries various things several times.

          • Yes, there is no way to edit the URL. I can understand this from a user point of view, in the backend just changing the URL is not enough though. A lot of information is cached that might change, so changing the URL is not much different to creating a new calendar. The workaround is pretty easy though.

          • The first time, when I installed lightning, it took multiple attempts to set up calendars, as the instructions are scarce and are not very clear (and I consider my computer/software skills way above average). This is especially true in regard to the “secondary” calendars (where people have more than one Google calendar).
            So, it took several trials before I could set it up correctly.

            After installing the broken combination of 24.1 and 2.6, I also did some fiddling before giving up.
            So, going like a monkey through the “add calendar” dialog each time was rather frustrating.

            Hence, sorry, but the low importance given to being unable to edit the URL is based on a vanilla scenario, which is often not the case.
            I am sure some users gave up while trying to set up their google calendars, and you’ll never hear from them. “Out of sight, out of mind”. Right? ;-)

            I’ll stop on this thread at this. Just wanted to let you know what you might be underestimating.

  18. It’s not working.

    I have changed about 5 of my calendars to the new link, and they still all have the yellow triangle. :-(

    Another “fun” thing that is happening, is that Thunderbird’s add-on manager keeps displaying the message “Lightning will be updated after you restart Daily” – even though I have restarted Daily 3 times, and it is the most current builds of Lightning 2013–09-24) and Thunderbird/Daily (27.0a1 (2013-09-24)).

    I need my calendars. Please help.

  19. I just updated to TB 24 and Lightning 2.6 and I’m also getting the yellow triangle with error message “The calendar Google Apps is momentarily not available” when I try to “Reload Remote Calendars.”

  20. It’s not working here.
    I still get the warning that calender is momentarily not available.
    Two questions: Do I nedd provider for google calender?
    I never used it before.
    And how can I access my other calnders, which url do i need there?
    Just insert the CalId like you mentioned above?

  21. Same problem here. Upgraded to TB 24.0, and Lightning 2.6, and lost access to my calendars. I followed the instructions to update the caldav URLs, but still no access.

    I imagine that there are a HUGE number of people using google+caldav that have lost access to their calendars because this upgrade. Very frustrating.

  22. Having the same problem. I did everything as I was told by Google, but all my calendars keep showing to me their yellow triangles. What can I do? I need back my calendars! Quite annoying.

  23. I have the same issue: I updated to TB 24.0, Lightning 2.6 and google calendar provider 0.25. I even deleted the calendar and recreated it using the new CalDav url. It started
    authenticating properly, and it created it, but the small yellow triangle still displays with a message “Calendar is unavailable momentarily”.
    The XML link from the calendar setting works properly and displays the calendar contents, but when I accept new invites from people, I have to restart TB in order for the event to show on the XML accessed calendar!!

    Bottom line: Caldav doesn’t work, google calendar having weird behavior using XML links, i.e. partially working!

  24. My calendars all stopped working a couple of days ago so now I’ve upgraded thunderbird to 24.0 and lightning to 2.6 and calendars are broken using both the new v2 Caldav as described above and the old. :(

  25. I should add to my post above… that my google calendar login is myname@mydomain rather than or

  26. This blog was a mixed blessing. Found out why my calendars were unavailable. So rushed to set up new calendar with this procedure, but it doesn’t work! But no-one said that once you do this, on restarting Thunderbird gets stuck at master password login window!!!! See So now can’t use Thunderbird at all. But start in safe mode and disable Lightning. Then restart and turn off master password. Then restart and re-enable Lightning and restart. Now delete new calendar, then reset master password, then restart. Back to square 1!! Except every other add-on, theme, plugin etc disabled – what do I need, no idea :-( Set up couple of ics calendars to see calendars, even if can’t write to them.

    Confused why this master password bug was known 8 August, still not assigned to be fixed and not referred to in this blog of 16 September.

    The irony is that Apple Reminders (tasks in otherspeak) now works with Lighning 2.6, which Google tasks never did. So now I can manage to do things (tasks, reminders, whatever) but can’t set up meetings :-) Could this be a clever way to increase productivity :-D

    • Now I know why about a month ago I got stuck after enabling a master password. Gee!.. I wasted lots of time.

  27. Same problem here
    Yesterday I discovered Lightning had lost connection with my google calendar account (using Lightning 2.6 and TB 24).
    Today I finally managed to find this relevant post. I created new calendar in Lightning using the new URL but still not manage to sync.
    “The calendar xxx is momentarily unavailable” message is still active.

    It would be very dissapointing if I have to ditch caldav sync as I’ve tried google provider before and had many issues.

    • I would also like to leave one suggestion, if I may

      It would be handy if you could create a form in “create new calendar” wizard where users will fill-in only the nesessary information (e.g. google calendar account) and the rest (e.g. the google caldav server url) is filled by the form?
      I believe this would solve issues, similar to this one, in possible future changes as it could be handled by the developed and included in a minor release update.

      • I agree this would be nice. There were plans to do it (see bugzilla), but unfortunately the volunteer contributor has stepped down. Its a rather complicated feature and can’t be added in a minor release. Sorry about this!

  28. In a fix is presented, that works fine for me.

  29. I’m having similar issues to others here in that I’ve recreated my calendar as a CalDav with the new URL and perpetually have the yellow triangle and no access to read or write to my calendar. This is incredibly inconvenient as it is my primary work calendar and I haven’t been able to accept invites in days. Does anyone have a solution or know if one is forth coming? I’m really stuck here.


  30. I should also note that though I’ve never used the Provider for Google, I was so desperate I’m giving it a shot. When I set up the calendar using the Google Calendar option I get this error: [Exception… “[xpconnect wrapped nsIURI]” nsresult: “0x804b000a (NS_ERROR_MALFORMED_URI)” location: “JS frame :: resource://calendar/modules/calUtils.jsm -> file:///C:/Users/Zachary/AppData/Roaming/Thunderbird/Profiles/rua8esan.default/extensions/%7Ba62ef8ec-5fdc-40c2-873c-223b8a6925cc%7D/js/calGoogleCalendar.js :: calGoogleCalendar.prototype.uri :: line 214” data: no]

    No idea what that means, but is there a fix for that?


    • Got this straightened out, forgot to grab the XML address. Can’t accept invites though.

      Still really need to get Lightning to connect to google, as per my first comment.


  31. Having the same issue. Google Calendars not working anymore (for more than a week now). TB 24, Lightning 2.6, win7 64. Tried everything, reinstall of everything, no change on 2 different machines.

    Google CalDAV calendars are not working, no matter if I enter the new or the old adress.

    Please take care of this with a hotfix ASAP, one can’t work without the calendars.

  32. Please allow me a question: Until now everything worked find. Because I used the “fg printers” to get a printed hourly timetable (which I need urgent for my work”, I cannot change to Thunderbird 24. The Add-on “fg printers” is not working with this version and nobody is developing further this genius tool.
    How can I use my Google-Calendar without the “Provider for Google”-Add-on??
    And does anybody know if the programmers will develop a version of Lightning that it can also print hourly timetables, so we will not need other Add-ons??
    Is there any place where I can place such a wish??

  33. This page ( talks about registering a new Project with Google Cloud Console in order to access the CalDAV API. I wonder if that could be why so many of us are having similar problems accessing it.

    Since I utterly refuse to give Google my cell phone number, I guess I’m screwed, since they require that to register a new Project. All of my Google Calendars just became useless. Thanks a bunch, Google.

    • Philipp Kewisch

      As you can see in the URL of the link, its targeted towards developers. As a user you do not need to register a new project with Google Cloud Console. Just use the new URLs as soon as the webdav-sync bugs are out of the way.

  34. Thanks for the response, Philipp. I sincerely hope you’re right. I wasn’t 100% sure what they meant by “send requests to the CalDAV API”, whether that meant hooking into it programmatically or whether it meant using it to pull data from the calendar system.

    I hope you guys can get the sync issues out of the way soon and get CalDAV working, because neither ICS nor Provider are doing the job for me – ICS is read-only, and Provider seems to have bugs of its own that prevent it from working on my system.

    While I’m at it, I know this is a pipe dream, but is there any possibility that once you get this issue resolved, you might backport the resolution to the latest version of Lightning that works with Thunderbird 12.0? I have an old, old laptop that I use mainly to keep the calendar available (it’s powerful enough for that), but it runs Windows 2000 since it’s not powerful enough to run XP or anything newer (it barely runs 2000) and version 12 of Thunderbird is the latest version that works on that OS. Without such a backport, I believe I’ve lost all two-way access to the calendars on that system due to Google’s “improvements”.

  35. Calendar interaction with MS Exchange 2010 Servers is broken again. Every update I have made ends up breaking this.. :(

    The error is now as follows:
    An error was encountered preparing the calendar located at https://auto/93a22c0a-7b79-47ef-a671-14917fbf39d1 for use. It will not be available.

    Error Code: 0x80570015

    Description: [Exception… “Component returned failure code: 0x80570015 (NS_ERROR_XPC_CI_RETURNED_FAILURE) [nsIJSCID.createInstance]” nsresult: “0x80570015 (NS_ERROR_XPC_CI_RETURNED_FAILURE)” location: “JS frame :: resource://calendar/modules/calUtils.jsm -> file:///home//.thunderbird/t7gc7j5f.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/calendar-js/calCalendarManager.js :: cmgr_createCalendar :: line 474” data: no]

    • This rather looks like the Linux issue we have been having, please see the more recent posts in our blog.

  36. hi,

    is there a way of knowing when a fixed release version of lightning will be available through the channels the occasional user is accustomed to?

    Many Thanks,

    • The answer is usually “as soon as we can”. You should be getting automatic updates through, Lightning 2.6.1 is in the queue for being released.

  37. Just wanted to say thanks so much for the details instructions and for giving a workaround for every possible problem. It’s much appreciated.

  38. Hello,

    I am using TB24.0, Ligthning 2.6 and Google provider 0.25.
    I am facing a bug with the search feature of Ligthning.
    When I entered a regular event (let’s say each monday from 9h to 10h), I see only one entry when I used the search event feature.
    I can see all of them if the view is set to “current month” but if I am looking for “all next events” or ” all events”, I can see only the first event.

    It seems to be a bug as all occurrences does show well when the view is “current month” but they do not show up when set to “all events” which is annoying I may need to search for all events in the year.

    Is there any plan to fix this ?
    Is there any lightning database to file that bug ?
    Is there any beta version available ?

    Thanks for your support.

    Note: That’s the very first time I am posting such request so I do not know the correct way to move forward.
    Moreover, I am using the french version of the tool so the word I used to describe the bug may be different to what you may see in the English version

    • Hi Christophe,

      the problem with this is that it would be impossible to expand “all events” for some recurring events. Lets say you have a Birthday event, which you have set to recur yearly on a certain day forever. To show “all events”, we would have to expand this until…forever.

      Therefore filters without an open end date show only the master item (i.e the first occurrence) and those with a definitive range show all expanded occurrences.

      I’m sorry this is a little confusing.

  39. I am also still suffering from the dreaded yellow triangles…

    I get the following error in error console:

    Tijdstempel: 7-10-2013 12:23:20
    Waarschuwing: Gebruik van getAttributeNodeNS() wordt niet meer ondersteund. Gebruik in plaats daarvan getAttributeNS().
    Bronbestand: resource://calendar/modules/calXMLUtils.jsm
    Regel: 32

    in english:
    Timestamp: 7-10-2013 12:23:20
    Warning: Use of getAttributeNodeNS () is no longer supported. Instead, use getAttributeNS ().
    Source File: resource :/ / calendar / modules / calXMLUtils.jsm
    Rule: 32

    maybe this will help…

  40. I had the same problems with my gmail calender but now it seems like the problem with the yellow triangle is fixed.

  41. On Thunderbird 24.0.1 with Lightning 2.6 and Provider for Google Calendar 0.25, when sending invitations selecting from Contacts list, invitations are not send because invitees are not preserved. Though invitations are sent correctly if you select your invitees individually from your Contacts. Prior to above mentioned upgrades the functionallity was working correctly.

  42. This is so useless……I tried a lot of “fixes” nothing. Outlook works … switching from Linux Mint 15 back to something that works.

  43. as of today october 25, my lightning stopped working ( it automatically updated to 2.6.1 ) – now i neither can edit existing calendars ( does NOT matter which type of calendar ) nor add any new calendar – my google calendar is not showing any more…
    Lubuntu 13.0 with TB 24.0 and Lighning 2.6.1

  44. […] y la versión 24 de Thunderbird con la 2.6.1 de Lightning ha dejado de funcionar. Te lo explican todo muy bien aquí, así como una solución temporal (usando versiones beta de ambos productos) por si no puedes […]

  45. Has Google forwarded the old addresses or something? Seems like the old calendars with the old caldav URLs have magically started working again- does anyone know whether this is permanent and we no longer have to worry about changing over to the new address/authentication?

    • Philipp Kewisch

      Hmm not sure. I havne’t heard anything. I might be able to translate the old urls internally for Lightning 2.6.3.

      • Philipp,
        As I pointed out in my comment from October 15 (above), with 2.6.1, the old API worked, at least from October 15 on.

        Now, for a change, – with 24.0.1 + 2.6.2, and with 24.1.0 + 2.6.3 (updated today), – the NEW URIs do not work, but the old ones still do. (It is on a Win7 box)
        The errors and warning are:

        [JavaScript Warning: “CalDAV: Unexpected response, status: HTTP/1.1 507 Insufficient Storage, href: /caldav/v2/”]

        [JavaScript Warning: “There has been an error reading data for calendar: MYCALENDAR. However, this error is believed to be minor, so the program will attempt to continue. Error code: DAV_REPORT_ERROR. Description: There has been an error reading data for calendar: It has been disabled until it is safe to use it.”]

        [JavaScript Warning: “There has been an error reading data for calendar: MYCALENDAR. However, this error is believed to be minor, so the program will attempt to continue. Error code: READ_FAILED. Description: “]

        [JavaScript Error: “[calCachedCalendar] replay action failed: null, uri=, result=2147500037, op=[xpconnect wrapped calIOperation]”]

        Which storage is this about? There is enough space on the local disk, and I don’t have much stored in any part of my Google account. Could it be something related to a local file that got corrupted or got wrong permissions (and cannot be written to)?

        Any clue as for why the new ones do not work, and what to do?

        Just found this bug report:
        Is that it?
        Any cure yet?

  46. Hello, is it possible to foresee when this issue will be solved? I also keep on having the problem even with the newest versions and trying the work-around you described above. Thanks for answering in advance! :)

    • Philipp Kewisch

      All Problems will be gone when Thunderbird 24.2.0 will be released, but you can get working versions now already.

  47. Thunderbird 24.0.1/Lightning 2.6.1
    My subsidiary calendars now work – although still with the old URL – but my primary calendar still shows the dreaded yellow triangle using both the new and old URLs.

    This problem also shows up on the google forum :

    • Same problem. TB 24.0.1, L 2.6.1, Win8 x64. The old address for my main gmail account still worked, but decided today was the day to delete all calendars and start again with the new improved CALDAV V2! Tried primary accounts secondary accounts, following the instructions as far as I could interpret them. All I get is the little yellow triangle. Now I can’t get iCal to work either!

      Is there anywhere a clear set of instructions as to what one enters, when and how. For instance, if you create a calendar under one email address, but are logged into Google under another, it will use the logged in email to authenticate the calendar, which I guess doesn’t work? Idiots guide for setting up Lightning and Google anywhere? I haven’t found one yet!

      • Sorry, I was panicing the iCal problem went away with a restart to TB. Now on TB 24.1.0, L 2.6.2. Still got the little yellow triangles with CalDav. If it is any help I have an “Assert failed: unexpected endbatch” :-(

  48. I’m soooo confused. I have Thunderbird 24.0 on a Dell AMD computer running Ubuntu 12.04. Is has worked fine with Lightning until now. I have no calendar. I have Lightning 2.6.1 and this blog seems to say that I must have a new version of Thunderbird in order to have a calendar and to sync it with my Google Calendar (which also syncs with my iPhone). But how do I get the new Thunderbird? Other sites say it isn’t out yet! Ubuntu usually updates automatically, and it hasn’t updated. Where is this mythical update and how do I get it into my computer?

    • Philipp Kewisch

      Sorry for the confusion. Ubuntu has not packaged the latest version of Thunderbird, which can be downloaded on Unless you are using Google Calendar via the CalDAV option, in your case, I’d suggest downgrading Lightning to version 2.6.

      The details: will give you Thunderbird 24.1.0, which will require Lightning 2.6.2, which has not been reviewed by the team. I assume this will make it even more confusing, so its probably best to do what I suggested above.

      • I think I’m using Provider for Google sync. To downgrade, do I remove 2.6.1 and install 2.6? Thanks.

  49. What did you do? I’ve reinstalled Lightning 2.6 and Provider 0.25, configured the private XML but I still cannot have Lightning working on Ubuntu 13.04.

    • Philipp Kewisch

      Please check your Thunderbird version. I think Ubuntu has upgraded to 24.1.0, so you need Lightning 2.6.2.

  50. For those using multiple calendars, here is what you need to use the v2 API directly. The red herring is thinking that your e-mail address will link to all calendars. In fact, according to that will just link to your default account calendar, so one unique URL, one calendar. Here is the section that helped me from the link above


    Where {calid} should be replaced by the “calendar ID” of the calendar to be accessed. This can be found through the Google Calendar web interface as follows: in the pull-down menu next to the calendar name, select Calendar Settings. On the resulting page the calendar ID is shown in a section labelled Calendar Address. The calendar ID for a user’s primary calendar is the same as that user’s email address.


    Use the calendar ID that looks like a random e-mail address instead of your actual e-mail address to subscribe directly to those secondary calendars. Don’t worry about the warning of setting it public for the links nearby, that is unrelated. You will be prompted for your google login credentials.

    • Thanks for the information, Sean. However, I cannot find the “random e-mail address” you mention. The only calendar ID I see is the one that uses my actual e-mail address, and I can’t seem to find any link that leads to the random-seeming address. How does one obtain this information?

  51. Let me be the first to congratulate you on fixing the Google Calendar problems in Lightning 2.6.3. The little yellow triangles seemed to have gone away. Many, many thanks, and well done :-)

  52. When I created the google calendar in latest TB it opened google page to confirm access. I confirm and calendar works for some time. After some time, calendar DC and shows warning sign. Not possible to reconnect.i had delete and re created again. but i found the same problem. any idea ??

  53. Thank you so much for this post – you have solved an issue I have had with Lightning for about a year!

  54. Lightning 2.6.1/Thunderbird 24.0.1 (Windows version)

    Hopefully a solution for your users like me whom have multiple Google accounts with multiple calendars in each and have had problems since Google changed to the new v2 API’s (yellow triangles).
    When using the v2 API URL and you get to the stage of authenticating your Google Account from the popup window that appears and it asks you to ACCEPT Lightning’s access to your calendar, Please look to the top-right of that popup window to make sure its logged in to the same Google Account, the calendar you trying to access is in. If it is the wrong Google Account , click on your name and sign out. Then sign in with the correct Google Account.

    I had the problem where after creating a calendar entry in Lightning, the entry would be ghosted and no tick in the box.

    I took this as Google still messing with their API and have had this ghost problem for many a weeks. Until tonight when by change I notice it was signed in to the wrong Google Account in the popup window.

    I have 9 calendars from 3 different Google accounts. After noticing this glitch all my calendars are now using the v2 API URL’s after making sure I was signed in to the correct Google Account for each calendar entry created.

    The problem is either Thunderbird or Lightning remembers the last authenticated Google Account and assumes all your calendar creations are from that same Google Account, which is perfectly fine for the 1 Google Account holders out there.

    PS: Thank You for a great Calendar project, been using since inception .

    (I hope the new v3 API from Google doesn’t cause as much issues for you when activated)

  55. hello
    i am not the only one but many person ( you can see both news group) that need a free part program not only extension
    and why not creating the sunbird 2.6
    nowdays having manger program a ppart become a must have
    and we suggest on future release to intodice the eisenhower matrix and the GTD
    this will give and exellent push to sunbird

  56. Does this API support account related calendars ?

  57. Anyone using Dual Stage authentication?
    I created a unique APPLICATION PASSWORD for LIGHTNING but have no place of entering it.
    I get the Authentication request for the Application to access my google account info but afterwards I see no changes in the calendar and it does not sync. I would assume that it needs the unique key that I generated for this application specifically, but I have no means of associating it with the calendar account.


  58. I’ve been using the Google Calendar provider and I tried your technique for the same account. Basically, Thunderbird just stopped responding. (Not exactly true, but it was 30 secods to 1 minute to get it to respond to anything and 4 minutes to get it to delete the account I just added.)

    Thundebird: 24.2.0
    Lightning: 2.6.4
    OS: Fedora 20

  59. […] Additional information are provided on Mozilla's Calendar blog. […]

  60. I am also still suffering from the dreaded yellow triangles…

    • Philipp Kewisch

      This should be fixed in Lightning 3.3, even without the Provider for Google Calendar. Check for updates tomorrow, it should be available with Thunderbird 31.

      • Actually, it was gone with the latest version just before 3.3 (although almost every time I switched a network location I got a window asking to accept authorization again). With 3.3 I am suffering from this again :( (using CalDav – not Provider).

  61. HELP!
    When the change in Google’s Caldav was announced last year I read the instructions at, and I did what I was told and inserted the following string into my Thunderbird 31 (I no longer remember where): Now when I launch Thunderbird I get the messages: “Add security exception: You are about to override how TB identifies this site. Site is attempting to identify itself with invalid information”. Then it provides exactly 2 choices: “Confirm exception” or “cancel” I choose the second but that means the same thing will happen when I next open TB!
    Thanks for any help to get me out of this because it has locked my Gmail from simple use.
    >I am on Win 8.1 and TB 31.

  62. Configured to sync via the URL it doesn’t work on T-Bird v17.0.8 / Lightning v1.9.1 but the same configuration syncs perfectly fine on the old stand-alone Mozilla Sunbird v0.9
    What’s the difference? Why the one and not the other?

    • Google is changing their endpoint and has deprecated the old URL format. Eventually they will shut it down. Thunderbird 17 is already very old, I’d suggest upgrading to Thunderbird 31 and using the new URL format.

      • Provider for Google Calendar is broken. Sometimes it works, sometimes it doesn’t. I tried deleting the Calendars in Lightning, and then adding them back – procedure doesn’t work. Till this gets fixed, I am using a browser to access my calendar. Lightning with provider for Google Calendar is too unreliable to trust. I am frustrated.

  63. Has something changed again recently?

    Yesterday I got a bunch of Google pop-up windows in TB/Lightning asking me to put in my various Google credentials but calendars don’t seem to sync properly anymore.

    I have tried adding calendars back in using xml and ical links. Adding as CalDav does not sync anything (I guess consist with your warning of it being deprecated).
    Adding with the ical addresses, they appear once but don’t seem to sync (warning flags and tooltip that says calendar is temporarily unavailable).

    When I next open TB, Provider asks to fix the calendars so that they are not read only but then they immediately give the error of being “temporarily unavailable”.

    Selecting the google calendar option in the New calendar window does not seem to recognize my sessions and when I add an email address, it does not list the available calendars.

    Any help would be appreciated!


    TB: 31.2.0
    Lightning: 3.3.1
    Provider for Google Calendar: 1.0.1
    I have 2 part verification enabled in case that is relevant…
    TB has an app-specific password set.

  64. thanks
    Eventually I succeeded
    disabling Provider for Google calendar
    connocting in Caldav mode to (notice that I used «googlemail» instead of «gmail»
    Due to Google way of life I fear that the connexion fail again some next day….

  65. This is not working for me – but there seems to be an obvious reason why: There appears to be no opportunity to put in my Google username and password!

    I’ve searched everywhere for this, but I must be missing something so obvious that I can’t find it. Please help.

    Thanks, Mark.

  66. It is very critical that Google is not showing URL for CalDAV in calendar settings and Thunderbird Lightening does not have import option to add XML based calendar URL.

    I was trying to import my calendar with iCal URL and was not working. (It is a Google Apps account).
    Well, above URL is working fine. Kudos to CalDAV.

    • Philipp Kewisch

      Please re-read the dialog text. The XML url is no longer needed, you can enter your email to get a nice graphical picker.