One of the items that the IDEAScripting dialog lacks is a date picker. I recently saw a post on the IDEA forum that they had the script for one but for some strange reason weren't releasing it on the scripting section, so I decided to try and create a date picker for my use and anyone else that wants to use it.
The attached script has the code for the date picker along with an example of how to use it with a dialog that asks for the user to enter a date.
When you start up the example script you will have a dialog with two edit boxes where the user can enter a date: