Option to add new contact freezes up - won't work
I had the same error in my console when trying to edit a participant report on an older civi install and discovered this helpful post: https://forum.civicrm.org/index.php?topic=20598.0

It doesn't sound like you've got exactly the same issue, but it's an interesting clue - i.e. in my case, some db data was generating a page that had js issues, it was not a conflict problem. Of course, it might also be a red herring.

Regardless, you'll want to turn off any js aggregation and use your js debugger to dig down and figure out who's version of the datepicker is giving problems, and where the problematic data is coming from. Sometimes just looking at the arguments being passed might be a clue. My best guess is that the datepicker is gagging on some invalid date that got mangled on Civi upgrade.