User blog comment:Murkywater2/Wiki Achievement Problem/@comment-5469467-20130116234832

Not sure about this, but the problem may be to do with time zones. I think the counter is set to a specific time zone (maybe in the US or even GMT or something), and not necessarily your local one. I notice that in my time zone, the end of the "day" in the achievement counter is sometime late morning. Maybe the time at which you edit is a factor, idk.

This may not be the issue you're having (it's possible the counter is bugged), but I hope it helps.