g1smd - 8:01 pm on Feb 15, 2011 (gmt 0)
Content published in the UK from midnight to 8 a.m. UK time is sometimes credited with the previous days date.
Sometimes the assigned date is that as used in California, not that where the content was published.
Be aware of the time and date being served in the HTTP header. That may have a bearing on things, especially if you are hosted in some other country, different to whatever the domain TLD might hint.