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Hi, I've been using CalDAV on my Synology server to synch between my desktop Thunderbird instance and handheld without problems. I recently added my laptop as a third platform which synched fine. However now I am working offline (I have an Internet connection but no remote access to Synology), Thunderbird repeatedly comes up with the message:

An error occurred when writing to the calendar My Calendar! Please see below for more information. Error code: MODIFICATION_FAILED.

The error message is maximally annoying as it steals focus from all Thunderbird windows then hides in the background, making it look like the app has disappeared entirely.

I have Offline Support checked in the calendar properties. Platform: Windows 11. I've tried deleting calender_date\cache.sqlte as suggested elsewhere but that makes all my appointment disappear.

Hi, As stated in the title, how do you synchronize the Thunderbird calendar of two machines.

I don't want to do it with google and not with cloud applications. You can find enough about that. Can you help me?

Thanks in advance. Rob

https://prnt.sc/3egVc8h02Y4Q

Getting error Modifcation_failed when importing my exported calendar.

Opened the the error log (take a look at the link)

Just wondering what I am doing wrong and what can i do to fix this situation

I added my nextcloud calendars to thunderbird by choosing "Network Calendars". It shows them as writable but those calendars with are read-only in nextcloud. This makes it a unnecessary difficult and irritating to make them read only manaully. Shouldn't thunderbird detect that automatically?

Running Thunderbird v115.14.0. Edit single event. No [Save] button, only [Send and Close]. This doesn't appear for a recurring event, which displays [Save and Close]. Not good.

I need to create a recurring event in Thunderbird calendar, the event occurs every month on the 3rd last business day of the month. Is there a way to do this? Or, is there any plan to create such an event function?

Apologies if this has been discussed before here, but in Thunderbird 128.1.0esr (64-bit) the All Events option is missing for calendar searches, which means it is no longer possible to search past events, see screenshot.

Hopefully the All Events option will be reintroduced soon?

Thank you.

Is there a way to set/change the organizer of an event in Calendar?

I'd like to create an event but set someone else in my address book as the organizer to whom all event replies will be sent. This is useful, for example, when my account is limited to ME@localhost and my Mail Transport Agent does address conversions.

thanks!