Well honestly, that's just plain stupid.. It's still the 28th there in the USA, where I assume most of your customers are based. I had several hundreds of dollars worth of  items in my cart at the moment you ended it...  Not going to bother ordering now, just wanted to give you a clue about the rest of the world.   When you clarify your "28th" date/time is GMT only AFTER it's ended -- good way to annoy customers.