'Invalid dateundefinedundefinedundefinedundefined' displayed

In New general appointment when user inputs incorrect date in Appointment on, for example year=12345 (longer >4char) or a letter, below Invalid dateundefinedundefinedundefinedundefined is displayed, what doesn't look nice.
Also, if user deletes at all the date he has inputed, this Invalid dateundefinedundefinedundefinedundefined is displayed also.