Just wanted to add that we too are having a tough go with the stats. I will give as much detail as I can to help trouble shoot the issue. Approximately one month ago we were having an issue with stats ending at 11:00 PM Eastern. I verified the wordpress setting for clock was set to New York. I also went in and made sure the server clock and php settings had the correct time settings. I believe the server clock was off by one hour. We corrected this and the stats began working correctly.
When the Daylight Savings Time Shift occurred the stat's day end shifted to 1:00 AM. I double checked clock settings in wordpress, php server as well as the site server. All were correctly showing the propper time. I went in to wordpress and updated my timezone setting from New York to Nassau, saved and then switched right back to New York and resaved. This corrected the issue.
Then four days ago, the stat's day end switched to UTC. By updating the wordpress timezone settings, I was able to get accurate (or at least I think is accurate) stats for that day.
Then we were unable to access stats while it was being worked on. The unavailable issue was resolved and then stats became erratic, sometimes ending on UTC and sometimes per wordpress timezone settings. When the number is off, I change and then reset wordpress timezone settings and it appears to correct the pageviews. I record the page views everynight so I can tell when it looks right based upon past history.
Currently the graph appears to be reading correctly, but the daily pageview display at the bottom left of the page is showing stats (most likely) from UTC timezone.
Feel free to contact me if I can help.