This seems to be an OS issue of setting date correctly on the PC.

Thanks for your reply, David. I'm on a mac and the date settings seem to be correct. The correct date is showing in other apps as well as in settings and on the menu bar. It's even showing correctly within Thunderbird settings (screenshot below). It's just showing all my email with incorrect dates and times. any thoughts on what else to try?

Okay, this is new ground for me and may prove nothing, but try the settings>general and experiment with the date formatting. It may be that this is incorrect.

Ok, the date formatting was showing me only two options, and both were wrong. It was allowing me to choose English (UK) or Engish (Afghanistan). I was able to add English (US) from the language menu below and then after I restared Thunderbird it gave me the option to choose English (US) for the application locale under Date and Time Formatting. Unfortunately, that didn't fix the issue with the dates showing incorrectly for emails.

Not saying this will help, but it might. Right click the folder, select properties and then the repair button. That regenerates the index file used to populate the lists, it might clear any corruption or oddities from the transfer from your old computer. This is especially so if the old one was set to a different locale

Thank you for the suggestion, Matt. I tried it and unfortunately it didn't fix the issue. If you have any other suggestions please let me know.

Did you download and install an English (US) version of Thunderbird? https://www.thunderbird.net/en-US/thunderbird/all/#E

Did you install any language packs ?

Is the computer Timezone set up correctly? Exit Thunderbird first. Please check computer Timezone as it should be for America New York - assuming that is your location. EDT — Eastern Daylight Time https://www.timeanddate.com/time/zone/usa/new-york

I note you have a 'Send Later' in the headers. Once you have checked Timezone is correct and restarted Thunderbird and same issue is still occuring, test to see if same problem when starting Thunderbird in Trouble shoot mode. Help > Troubleshoot Mode select Continue in Troubleshoot Mode.

Report on result.

Thank you Toad-Hall.

I deleted Thunderbird and the profile folder from my macbook, re-installed TB English (US) from the link you provided, copied my profile folder from my old laptop, and double checked my computer clock/timezone settings. As before, thunderbird is showing the year as 1402 on my emails. The issue persists in troubleshoot mode as well.

Thunderbird gets it's time and date from the computer settings. So I think something is not set up correctly.

I did locate this question where someone had wrong date applied to all emails like you. They were checking the Language & Region and specifically the formatting of date. https://support.mozilla.org/en-US/questions/1153644

So have another look on computer - something is not set up correctly for apps when it comes to format of date. Maybe this link will be of help. Please work through these particular settings making sure they are set up correctly. https://support.apple.com/en-gb/guide/mac-help/mh27073/mac Change how dates, times and more display on Mac You can change the formats used to display dates, times, numbers and currencies in Finder windows and apps, such as Mail.

Ok, that did it! Thanks so much for your help, I really appreciate it