Moment.js is cool alternative to Date.js. Not that I have any grudges for Date.js, Date.js is an equally cool date time plugin, only because I ran into some issue as stated here have I decided to ditch Date.js for Moment.js. Here is a list of all good date manipulation javascript plugins.

You can check out the documentation for moment.js here, or dive straight into their source code here(Minified Source &
Full Source).

For ASP.NET MVC developers there is a nuget extension available here. To use Moment.js with ASP.NET MVC.

Below are few examples I created using Moment.js, here is the fiddle link.. go check em out !

Hope this helps :)