What type of calendar - local or network? If network, is it a Google Calendar? If a Google Calendar, how do you connect to it - via CalDAV or the provider add-on?

network. outllok.com. i imported the share link into thunderbird

I don't know much about outlook.com. How do you access the outlook.com calendar? Via CalDAV, or do you need an add-on?

Just to confirm, are we talking about an outlook.com calendar (former Windows Live) or a calendar on a MS Exchange server?

cal dav and correct windows live

Error code: MODIFICATION_FAILED Description: Status Code: 2147500037, The request cannot be processed. Server Replied with 403

Lightning 2.6.4 TB 24.3.0

Yahoo calendar

5 events will not clear when I "dismiss" or "dismiss all".

ypma, I think it would be better to raise your own topic, as your problem is apparently about a Yahoo calendar, not outlook.com.

I'm having this problem as well and I'm using a local calendar. The two things that changed just before started noticing it 1) I have upgraded to Thunderbird 31.0 with the ungrade of Ubuntu to version 14 and 2) I deleted my gmail account in Thunderbird and re-added it to switch to IMAP from SMPT/POP.

Does anyone have a fix for this?

cjowett, please raise your own thread for your problem.