Howdy! I wouldn't have noticed it if it weren't for the fact that I frequently see someone else play this game too, but I noticed that my advent calendar and another user's are on different days?

My calendar is on day 6:


The other player's is on day 7:


Neither of us have purchased the premium calendar (I saw that some people got the first seven days unlocked when they did because it was meant to release earlier). Both screenshots were taken within the same minute or so.
I don't think it's a big deal because we'll both be able to claim all of the daily rewards before the end of the festival, I just thought it was weird.

Edit: I'd also like to note, I claimed the first advent award immediately as it was released, so I wouldn't have been a day behind even if it let me claim the reward late.

This is probably because this system, unlike the advent calendar, does not skip days. For example, if you claimed a prize and then did nothing for two days, you would come back to the next prize being available, not the one ahead of it.

After claiming a day's reward, players must wait until 12:00 AM daily to claim the next day's reward regardless of when they claimed today's reward.

As pointed out above, it will be different for each player. If you have the Premium upgrade, then you can claim all prizes up until what's Available. Otherwise, you can only claim one day's prizes per day. If you don't claim a prize for it day, it will remain locked until you claim it. So you essentially have to login and claim prizes on 12 unique days of the Festival, but it can be whatever 12 days you want.

Ahh, I must have missed a day and not realized it then. Thank you!