Small issue, but the inconsistent behavior does suggest a bug.
The learning calendar seems to always be synced to the memrise standard time zone even if you change the time zone in which you live/operate.
Notice in the image above, the calendar shows that I’ve done a number of events today, however I have no recorded entries in the two lessons I’m currently doing. I did that work last night (in the American evening). Based on memrise standard time, that would have been Friday, so that’s where it credited the time. When I did the work last night, it actually appears to credit my time to the void, because it stops crediting to Thursday, but doesn’t even show me Friday yet because it’s not Friday in my time zone.
Small issue, but I would call it bug because of the inconsistent way it behaves, using my time zone for some things and then using memrise standard times for others.