The most likely is that it's a combination of both (time zones and bot frequency). It would be best if someone from Yobit came here and explained what is the reason that some posts written in the middle of the day are counted on the next day.
Indeed the reason for this confusion with post count would be a combination of both: time zones and bot frequency.
I haven't got any problems with the counting bot the only thing I had to learn was that all posts which were written after 9 p.m CET will be counted for the next day.
Additionally, some time ago (28 October) in Europe we have the wintertime, so the clock is now turned one hour back, which makes now all posts written after 8 p.m CET to be counted the next day.