How to make a calendar widget?

I would suggest asking this over on the XDA forums

 

We've a perfectly good Application Development forum the OP could also ask the question in.

OP, I'll move the thread for you, you'll probably get a better response there.

 

XDA is not the best place to ask application development questions. XDA is more geared towards hardware and OS mods than anything else.

EDIT: @OP, the question you have asked is very broad. In fact, one could argue that it is too broad to properly answer. I can, however, recommend that you take a look at the DateWidget sample provided with the Android SDK.