UPDATE (March 14th, 2015)
When I first wrote this library, I didn’t have a great understanding of the ngModelController API, nor good directive design. So I wouldn’t recommend this library anymore. I started on a replacement library here, though it’s not quite ready for production use.
I wasn’t particularly happy with any of the datepicker directives out there for Angular.js, so I decided to build one myself. I did it out of a need on my current project but also because I wanted to learn the ins and outs of directives. You can find the library on Github.