The game displays Pacific Standard Time, or at least it does in forum posts, blog posts, etc.
CDP is based off of, I believe, Greenwich Mean Time, which is 8 hours ahead of PST.
If you played a game at, say 2:00 PM PST on the 21st, that would be 10:00 PM GMT, on the 21st.
If your next game was at 6:00 PM PST, the next day, on the 22nd, that would be 2:00AM GMT, on the 23rd.
In other words, WGT might tell you on your profile page that you played a game each day since the display is based off of PST, or you might simply be under the impression that you play one game a day, based on your timezone, but you did not play a game each day according to GMT. If it is not this exactly, it is definitely something like this. I'm not sure how it works; all I know is I get CDP at roughly 6-8 PM CST. It's not based on my timezone nor any US timezone.
Quintessential WGT programming... make something super cool, but screw up one tiny detail that breaks the entire thing... lmao! The quirks keep the game sorta interesting, though.