Is your Calendar settings configured to start at 8:00 AM  ?

I have the same version 140.2.0 ( on Windows 11 24H2 ) and it works fine for me.

Yes the Calendar settings are configured to start at 8:00 AM. I have just noticed that when I go to the email tab and go back to the Calendar : default view is set to midnight, and when I do the same thing again : the Calendar view goes back to "normal" (day time), I can ping pong between both views on and on. So up to now, I go back to my email twice to get the normal time view back on the Calendar, which quite annoying but the best I have found yet.

I see the problem now. Every times I switch from Calendar to email and then Calendar, it went back one hour : my calendar start at 08:00, switch to email and back to Calendar : it starts showing 07:00AM , back to email and then back to calendar : it starts showing 06:00AM and so on.

So you're right this is a bug.

I see what you experience, we both seem to have a bug related to the "Calendar time tracking" when we switch from Calendar to email : either going back one hour or displaying midnight/back to normal. By the way, yesterday, just before I had my actual "midnight display" bug, I experienced the "back one hour" bug you have right now.

I find are few weird things as well. Windows 11 OS and beta 143.0b2

I've set same settings as you. Calendar - first opens showing the start time of 8am etc I've selected 'week' view Go to emails and return - now it has moved forward so it's displaying the current time - just gone 5pm and maybe a couple of hours prior. This is actually really handy and probably the correct action.

I'm not getting the midnight crazy time.

However, after selecting several emails and then reselect Calendar - it's blank until I use the scroll to right and scroll back to left - go figure :)

I also discovered it does the same in 'Day' view.

So I'm not seeing the 'midnight' bug - I'm getting the real midnight - totally dark - shows nothing until a quick right and left scroll.

It seems there are a few issues. I'll do a load of testing all options and reselecting all kinds of stuff for test purposes and report as a bug.

It might be useful if you can check to see if anything is occuring in the error console. Empty the error console, then enable calendar and perform a few moves back and forth to see if something gets flagged up. Please post images showing what - if anything is in the error console - I'm not seeing anything in error console.

Interesting - does not occur if you just select different folders as opposed to selecting emails. Do you see the same ?

Hey - after selecting folders - I went back to selecting emails - now I've managed to get a half screen showing 7pm to midnight - :)

Can everyone please test - Help > Troubleshoot mode click on 'Restart' and select 'Continue in Troubleshoot mode'

Please report on whether it now works properly or not. For me - I managed to get the blank screen in Troubleshoot mode.

If it works ok then please offer info on what if any addon extension you use or whether you use 'userChrome.css' etc

To provide feedback : - I restarted Thunderbird 5 min ago and now I don't have the "midnight default Calendar view", I have the same bug as you : minus 1 hour every time I go onto the Calendar or any other tab I tried (the "Parameters" or "Add-on" tabs for example). I get this bug on both daily and weekly Calendar displays. - Nothing popped up in the error Console when I performed a few moves back and forth between the emails and the Calendar - when I test Troubleshoot mode : I have the "midnight default Calendar view" again. My only extension is "Send later" and I changed the overall display through the menu bar : display/Zoom and Density (I don't know if it changes the userChrome.css, but I did not change it manually is this is what you mean).

Troubleshoot mode click on 'Restart' and select 'Continue in Troubleshoot mode'

Result:

It's still behave like it did before meaning : it goes back 1 hour and eventually to 01:00 AM. I never got the Blank screen. It just stop at 01:00 AM. I have no Add on and don't use 'userChrome.css'. My configuration is pretty plain Thunderbird. No event showed up in error console during tests.

Thanks everyone for reporting and contributing to this issue which is obviously a bug. I've created a bug report. I'm posting a link below as people may want to follow:

• https://bugzilla.mozilla.org/show_bug.cgi?id=1986676

Thank you very much for your support and for creating a bug report, I will follow the provided link information.