I have a Mac Book (2006) All my saved emails for two and a half years have the same date. How do I get the original dates back?

Question

From the "date and time" I tried to drag the month and year to my menu bar. It did not stay, so I did it several times, but to no avail. I closed the window and went back to my Thunderbird email only to find that the date I tried to use became the date in the "date received" column of all of my emails from back to 2011. I changed the date a few days later, and then the date changed on all of my emails. I would like to undo whatever I did to the dates so that the emails show when they were originally received. I did manage to get "the order received" which helps a little, but I cannot see the original dates.
I have checked "Set date and time automatically" but it doesn't change the dates on my saved emails.

Answer 1

I at first thought it might be a Mac thing, but I couldn't find a solution. I realized that the date only affected my email, so then I thought it must be a Mozilla problem.