It doesn't appear "2010" is the culprit. It's the formatting of "December". Note:
After "2010" - no prompt:
With today being
"December 1, 2010", that's the prompt you'll get.
Tomorrow, when you type "December" you'll get the prompt for "December 2, 2010".
The specific date format presented in the prompt has to do with your local settings in Windows itself.
More info here...
Changing the default country/region in Windows changes the default format for numbers, currencies, time, and dates to those usually used for that country/region. For example, if you want to change your default measuring units from centimeters to inches, or display a date as 2009/10/31 instead of 10/31/2009, select the country/region where you are located and the standard measurement systems used in that location are applied to your computer.