There are lots of ways to write dates in English. The American English way (month first) is not the only way. In England, for example, 9/11 means 9th November, not September the eleventh.
But quite a few people on Duolingo have date-format-change-itis when it comes to revising translations. They see 20th February 2015 and they revise it to February 20, 2015.
When someone revises a translation, in my view, they should be looking to correct mistakes or improve the accuracy or the wording.
Changing one date format for another is not revising a translation, if that's the only change you're making.
Twentieth of February - February the twentieth - both are perfectly ok 20th February 2015 - February 20th, 2015 - ditto 20 February 2015 - February 20, 2015 - same again 20/2/2015 - 2/20/2015 - no problem with either of these.
I could go on... but life is too short!
Yea, I hate it when someone edits your translation to write the date differently -_-
The first ever translation I did involved some kind of date, and I wrote it in this format "20th February" but someone edited it to "20th of February". At the time, I thought this was just the DuoLingo standard way of writing it, so I thanked him for showing me how to do it properly.
But a couple of weeks ago (last time I did a translation sadly) I wrote it in the above format and someone edited it saying that it was too long, and wrote it the way I initially did.
I didn't actually do anything, couldn't really be bothered, but next time I see the date being edited by anyone on a translation, even if it isn't mine, I'll re-edit his back to the original. Same goes for other pointless changes to be honest, too many small irritating edits have started to take their toll on me, and they need to be stopped! :P
Sometimes people aren't aware that other formats are correct. When I translate something like that, I will add a comment saying "U.S. date/time format". If people still change it, well, it's not worth getting worked up about. I ignore it and move on, or if it's one person persistently changing everything from AmE to BrE (or vice versa) I might write on their activity to let them know they should stick with the original unless it is actually incorrect.
I'm pretty sure our global society is doomed while we have terrible hold-over issues like this. Fortunately, there is a solution: https://en.wikipedia.org/wiki/ISO_8601
It sorts nicely in computer-based systems. It is non-ambiguous. It seems to have been based on common sense.
Thanks & good luck!