Did you try to change in edit -> preferences -> mail preferences -> headers -> date/time format ?

Yes I did. When viewing an individual message, the date shown in the message headers is in the correct format. Still, in the folder listing, the dates shown next to the subject lines are in the system locale format, and there seems to be no way to change that.

I tried to reproduce it, and the Table Column is the value to be used in the message list (not folder list, with which I believe you meant the message list). The problem might be that there's used the %ad, which is for "abbreviated date", and when it's more than a week it turns to a locale default date format. Not using %ad allows to use any date format, in a price of loosing Today/Yesterday and so on.

Maybe having a way to specify the date format for the %ad might do the trick.

I just found out that one can change default formats in
   ~/.local/share/evolution/datetime-formats.ini
by adding into the [formats] section line like this:

   Default-Date=%Y*%m*%d

which can be done only when evolution is closed (it overwrites the file on close with the content it had when evolution was opened).

Nonetheless, I made an improvement to allow additional "argument" for the %ad format. When it's followed by a text in [], then it is used as a format for the date, instead of the default format. Thus it can be something like this:

   %ad[%d.%m.%Y] %I:%M %p

Created commit a4fbe506ae in evo master (3.31.2+)