I think it could be a timezone mistake if it was a 12 hours difference max. But this is at least a 19 hours difference, so I don't think time zones could be responsible for that. I'd say it's a proper bug.
Strange. Can't really tell why that showed for 'tomorrow'.
I've also set my clock back to the time of your post, but here it showed 'yesterday'.
Don't know!
Let me know if you see it happen again. It might be another 361 days though - I figure it had something to do with the transition of the year. Our own y2k16 bug.