Got the same problem.
(My “busiest day” used to be 784, and they now name last Friday’s, a 273 day … grrrr!)
I hope that it will be repaired automatically on Monday, when wordpress support is back.
Thanks, all, I didn’t even notice that my “busiest day” has been changed to last Friday also.
That wasn’t even my busiest day last week and not even close to my really busiest day that was sometime last August. Even if this glitch gets fixed promptly, how do we know that the rest of the stats are credible?
I’ll check back tomorrow to see if it’s fixed before contacting Support.