Apologies if this has been covered - I've been traveling the last week using my iPhone and iPad instead of the web site.
So, here's the deal. It's 11:45pm in my time zone (US Central, DST in effect). The current date is 5/22/2010. The date and time are showing correctly in the Windows 7 task bar and several desktop gadgets.
But, when I view my To-Do list in Firefox 3.6.3, everything with a due date of 5/23 says due "Today", and everything with a due date of 5/24 says due "Tomorrow".
FYI & FWIW...
Oh - one other note. Most of the iPad and iPhone usage was from in the eastern time zone.
The website doesn't know that you are view it from a different timezone unless you tell it by going into your account settings and updating the timezone. Once you do this, the time and date will be adjusted for your timezone.