The message doesn’t use a localized date format. I can fix that quite easily. Fixed in UX: Localize date format in "new user of the month" message · discourse/discourse@1121514 · GitHub
Because the badge isn’t granted at the end of the month, but at a monthly interval starting at the time the badge was granted for the first time. That way it’s possible that you get the badge at the beginning or middle of the month. I find that highly confusing.
@eviltrout Was that supposed to happen or would you like me to fix that as well?
Also, the grant date seems to shift by roughly 1 day each month. On Meta it looks like this:
granted_at
2019-02-21 01:11:28.219231
2019-02-21 01:11:27.567236
2019-01-21 23:55:59.212397
2019-01-21 23:55:56.144663
2018-12-22 22:17:24.405719
2018-12-22 22:17:24.153355
2018-11-23 03:44:18.793055
2018-11-23 03:44:18.574876