Hi, I am back again, hope you aren't groaning to loud.
Using datepicker from https://angular-ui.github.io/bootstrap/, 0.13 or 0.13.2 both do it so far.
Angular v1.3.13
Plunker - http://plnkr.co/edit/ykWiwvOJbNvKYdVwXrhY?p=preview
If you select a valid date, after the validation timeout it flags it as invalid, if you leave the field causing the blur to trigger it clears the error, but does not clear it until you leave.
The problem also occurs if i just paste a valid date into that example not use the datepicker function directly. Or type a valid date in it will bring up error. If I edit the date once error is up it will clear the error once the edited date is valid again. If I leave the field [blur] with error up it will clear the error, but the error will not go away if i don't do something.
Here is the spanner in the works. If I remove datepicker from that plunker entirely pasting in a valid date does not cause the validation error to come up.
No Error Plunker without datepicker - http://plnkr.co/edit/yBZZFzTiVOmPaDwlAAYL?p=preview
I can fully understand if it may not be something you can influence, however I suspect datepicker may be in wide spread use it may come back to haunt you later :).