A load of those emails are threaded which means it's showing the date of the original thread. But, I do not know if that was the date of the original thread nor whether the last subthread is showing the correct date because the image does not show any expanded threads. However, I do notice that all those emails are saying the year 2002. So, I'm going to assume all those emails with threads are very recent. Looking at the image you supplied the date in top right corner does not mention the year - just the day and date and time - all of which seems ok, but it doesn't tell me if the year is set up correctly. As Thunderbird gets the date from the computer I'm guessing you have something incorrectly set up in the computer. Exit Thunderbird and sort out everything listed below: Please check the computer date and time settings. In particular the year. check you have got the correct 'timezone' set up. check the Language and Region settings. Useful links: https://support.apple.com/en-gb/guide/mac-help/mchlp2996/mac https://support.apple.com/en-gb/guide/mac-help/mh27073/mac