I'm long time user of Thunderbird Calendar. For most of the events in calendar I have reminders that should pop up for example 7 days before the event. This was working correctly. About half year ago. The reminders stopped working. I don't get the reminder 7 days before, but they pop up on the day of the event. This is quite unpleasant. For example If I have my car technical check deadline and I get the reminder on the deadline, not 7 days ahead. I have not changed any settings around the time it started happening. So far I have checked: -Individual event reminder settings : yes they still got the reminder set up to pop up some days before the event -Settings / Calendar / Reminders / Show the reminder dialog - checked -Settings / Calendar / Notification / Show notifications for upcoming events - I added here "1 day before event starts" notification, but that also doesn't work. -Tried Googling the issue. Found some threads about reminders not popping at all. Not the case here. I don't get notifications before the event, but they pop up at the time of the event. No luck here. Since about half a year has passed since this started, I guess it's not a bug that happens to everyone.