A field of type Datetime can be configured to leave the time away, for cases where you are only interested in the date.
Unfortunately, I need the opposite: A time field without additional date. But it seems not to be possible to configure Datetime to leave the date away. Is there a possibility to do this? Or any alternative, e. g. a module? Of course I simply could use text fields for time input, but I would prefer the nice time picker and automatic input validation.