Hi,
I use the french translation of Discourse and I found some strings that I can’t translate in the customize part of the admin panel.
“Primary email” when you try to register an account with a blacklisted email domain.
“of” when you click on one image in a post with multiple big images to see it in full screen.
“to” and the entire list of periodicity in the insert date menu.
The display of the month is in English in the message sent for the new user of the month.
I also want to point out that you can’t change the format of a selected date in Advanced search and the Insert date menu (It’s not readable for a french).
How is YYYY-MM-DD not readable for a 
?
I know we mostly use DD-MM-YYYY, but I find YYYY-MM-DD easy enough to read (I actually prefer that format, but that’s just because I’m a geek).
The to was made translatable by @eviltrout in
https://github.com/discourse/discourse/commit/34b871a86c2ddff9ffd0205095a2018c336923b9
Sorry, I mispoke. 
It’s readable but it can be confusing because we don’t use this format. For example:
March 9, 2019 = 2019-03-09
A french may wonder which of these numbers is the month and which is the day. I’m pretty sure my grandmother can’t read that kind of format.
I blame the 
for coming up and using the butchered MM/DD/YYYY format.
Was it really the US? I would expect we inherited it from the UK like imperial units.
US/UK, is there a difference? 
EDIT: looks like you’re right. The UK did invent that format but they regained their sanity in the 20th Century thanks to the 
.
I added the missing translations for the lightbox in https://github.com/discourse/discourse/commit/7e8579b8aaf551c2b9fa5eb2044017284c6270cc.
The “Insert date” dialog should already be fully translatable.
This was fixed in New user of the month: wrong month, not localized - #5 by gerhard.
Regarding the "YYYY-MM-DD` date format: As far as I can see our datepicker always uses that format. Changing that behavior so that it shows a localized date while making sure that nothing breaks will take a little bit more time. I’ll take another look at this at a later time.
