This last weekend was a double XP weekend...advertised from April 11-14. Now, any sane individual would conclude from that statement that if they logged in on the 14th, they should still be getting double XP. However, the event ended in the early morning on the 14th.
Either extend the actually playable time allowed to more closely match what it is that you are advertising, or change your advertising to be more accurate. This has happened every time there has been a double XP weekend, and every time you leave your users disappointed.