This is caused by an error in the JS code in
/libs/cq/ui/widgets/source/undo/UndoHistory.js (line 921).
There is an undefined variable “uu” used here.
This is a bug in CQ5.5 and will be fixed in a future release.
A workaround would be to add a definition for “var uu = CQ.undo.util.UndoUtils;” before that variable is called.
1. create an overlay of /libs/cq/ui/widgets/source/undo/UndoHistory.js to /apps/cq/ui/widgets/source/undo/UndoHistory.js
2. open /apps/cq/ui/widgets/source/undo/UndoHistory.js
3. goto line 921
4. paste the following code into line 921:
var uu =CQ.undo.util.UndoUtils;
5. line 922 should now have:
var dateValue =uu.parseDate(originalValue);
6. save the file