Noda Time use Mercurial for its source control system. A good alternative for Microsoft Windows uses is TortoiseHg which install shell extensions so that Mercurial can be used from the Windows Explorer.

Once you have Mercurial installed, you will need to make a local clone of the repository. The source address for the repository is:

https://noda-time.googlecode.com/hg/

You will need to use this in whatever tool you installed. From the command line you would enter:

hg clone https://noda-time.googlecode.com/hg/ noda-time

This will clone the repository to your computer under the directory noda-time.