More than you ever thought you needed to know about DateTime
DateTime is just a simple struct, right? How complicated can it be? Complicated enough to warrant a 12 page article about it, full of best practices. Most people take DateTime for granted, but there are some very important gotchas that usually don't come out in testing. I was bitten by one last year (XML Serialization and different time zones) and you could be, too. Read this, especially if you do web services.
Coding Best Practices Using DateTime in the .NET Framework