Date Localization in asp.net for user birthdays

Globalization and localization is a whole topic; you can start here: http://msdn.microsoft.com/en-us/library/c6zyy3s9.aspx[^].

Before looking at all that, would you rather listen to a good friendly advice: don't be silly and don't use traditional numeric formats for dates if your site is international. Don't chase this highly questionable national authenticity based on culture. Just don't — your users are not obliged to maintain right culture settings in their systems or browsers and are not obliged to even remember about such things. Those national settings are not rational at all and not respected by everyone; for example, English-speaking people use different date/time notation, depending on country and sometimes even personal preferences.

Instead, always write any dates in the humanly and human-readable way, such as:
December 28, 2011; 28th of December, 2011, etc. — if you use localization or not.

Don't allow yourself any ambiguity. Even if you use 12/28/2011, always mention it is dd/mm/yyyy or something. Be a human being!

—SA