The TimePicker TimeView resets the date portion of the component Value to today. This does not happen when typing in the DateInput.

The problem is with start-end validation where the start Value gets ahead of the end Value, even if the time parts are valid.

A possible workaround is to use the TimePicker ValueChanged event to override the date part to its previous value, or to set a fixed date value that is the same for the start and end TimePickers.