Regional browser options and effect of server side code

I have a international portal application that I'm experiencing problems with users who don't have their options set to English(US). For example I'm displaying a date in a label as a string in (mm/dd/yyyy) format. When I execute a CDate() function in the server code when the user has a different regional setting with a different date format I'm receiving errors on the CDate function. It seems like the PDK is doing some interpreting of the data before the CDate(). I'm also experiencing problems with decimals because some regions use a decimal and others use a comma. Is there a setting or some code that I can use to change the behavior?