The ExtJS 4.1 beta's Ext.Date doesn't seem to parse ISO8601 dates (format "c") correctly:

Code:
Ext.Date.parse('2011-12-10T00:00:01-05:00', 'c') => undefined
This parsed correctly on the 4.0.x releases. 4.1 seems to be trying to parse the time as a 12-hour time, instead of the ISO8601 24-hr format.