The client side JS should be faster and more efficient than anything on the server side unless you need to do some integrating with your data. Even then, you could probably combine them...
>>If you need, I have nice date range picking up Java Script module that you can edit and adjust for your needs. It looks like menu, but also it could be re-built to be a calendar.
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>I already have one. I was just wondering if WWC has one built in.