This question may be related to a resolved thread.
On Friday morning, I updated from ExpressionEngine 2.1.3 to 2.2.1, using a freshly-downloaded build from the store.
This morning, I added a date field to a new Safecracker template and ran into an issue where the DatePicker wasn’t rendering. Digging through the forums, I found the post below which suggested applying the hot fix from 5 July 2011.
http://ellislab.com/forums/viewthread/194359/#916380
Even though I was using ExpressionEngine 2.2.1 (Build 20110705) which, according to the link below should have had the fixed code in place already, I went ahead and installed the updated files after which the datepicker rendered as expected and my issue resolved.
http://ellislab.com/forums/viewthread/193320/
I’m curious if a file was missed when the update scripts ran?