What is the timezone for the count ?
Some people said it's GMT+3 (Moscow time).
The forum, by default, uses GMT+0; So if that's what is set for you, the next day is set at 21:00.
I talked to other users and it is not exactly GMT +3, because for some already around 19:00 forum time, counts posts for the next day. It probably depends individually for each user. It is possible that it depends on time each of us registered.