Lo so per esperienza, quando si arriva a dover gestire una data tutto si complica. Purtroppo esitono i fusi orari e tanti modi diversi di rappresentare le date, forse qui c'e' qualcosa che può aiutarvi.
Writing programs that store, perform calculations, and serialize time values using the DateTime type in the Microsoft .NET Framework requires an awareness of the different issues associated with time representations available in Windows and .NET. This article focuses on key testing and development scenarios involving time and defines the best practice recommendations for writing programs that use the DateTime type in Microsoft .NET-based applications and assemblies.
http://msdn.microsoft.com/netframework/default.aspx?pull=/library/en-us/dndotnet/html/datetimecode.asp