Sorry for the problem. We were only recently made aware of this issue, which occurs in games that have been running for a long time on machines with high-frame rates. While we have fixed the problem, unfortunately the patch will be part of ver 1.5.7 which isn't ready for release yet.
In the meantime you can try resetting the in-game date using the console (open with the tilde key '~') and the 'setday' command. Typing 'setday -abs 0' without the quotes should reset the day to the beginning and allow time to progress as usual. I believe this should be safe with the exception of any active timed objectives - so you'll want to start the 'hold for 360 days' objective before you reset the date. If you have started them already you can also try 'setday 360' to jump the clock ahead so that you complete those objectives before resetting the clock.
Alternatively, I could also e-mail you an unofficial version of the game that includes the patch but hasn't been testing thoroughly yet.
Thanks for your patience.