My website is hosted on multiple servers at different locations
Everywhere the Culture of the data format is different- we use mm/dd/yyyy format every w
Never, ever, store dates internally as strings. Not in the database, not in your app.
If you need to move date values between servers, go binary. Or if you really really have to use strings, use ToString(CultureInfo.InvariantCulture) - or simply serialize the Ticks property.
Also, never pass dates as strings to the database using SQL commands that you build using code. Use SqlParameter for that, or even better, rely on some O/R Mapper, such as Entity Framework or Linq to SQL.