The option to clear a date input is replaced by a calendar icon, which makes it impossible to clear the field efficiently (with one/few mouseclicks/keypresses).
The only option I've found is by clicking a part of the date, press backspace (not even delete), tab, repeat.
The same happened to chromium, as discussed over here: https://bugs.chromium.org/p/chromium/issues/detail?id=1087501
Please reintroduce a clear option.