Useful extension methods C# library for the Date object

Question

Could you guys recommend me a library which handles the most common missing features for the Date object in C#?

.. Things like figuring out:

• What quarter a given date is in
• Get the start/end of a given quarter/month/week
• Various subtraction -and addition methods

Note: A library which implements its features as extension methods would be a plus.

Answer 1

There are some interesting datetime extension methods (especially for addition/subtraction) in this post: Post your extension goodies for C# .Net.
Check in particular the first answer for datetime-based extension libraries. The methods are being collected in a CodePlex project, maybe it's worth having a look.