Changing a "time" value from a valid to an invalid value will not trigger the "save" button to be disabled. When saving, the previously valid value will be saved.
The reason for this is that the jQuery.valueview.experts.TimeInput instance won't notify about the change from valid to invalid. Probably because the jQuery.time.timeinput's "update" event only triggers when the value changes to another valid value.
Note: this should be a bug in the "ValueView" extension which is not yet available in bugzilla.