Before I roll my own (again, I already did this once in Java), is there a date picker that allows predefined named ranges in addition to the standard user-chosen dates. For example, I want the user to be able to choose 'Today' or 'This Week' or 'Last Month' and store it in such a way that it's relative to the time I access it, not based on the date they chose it. Ideally this would be easily extended so if I wanted to add 'The Tuesday after Next' I would just write a little snippet of code and have it automatically added to the list. I still want them to be able to enter an absolute date as well.
I'd prefer a Rails plugin, but if there's a JQuery plugin that can do something similar, I could adapt it.