Try using a minus date.  As in -04/14/2021

Works in a lot of places in big sister software Lacerte.

Unfortunately, this is one incident where ProConnect Tax does not work like its big sister Lacerte.  Negative date, which defaults for "Various", is not an acceptable entry for this field at all on F.709.

Just put down a date for the gift unless you want to really break that up into different pieces.  Guess it's one of those come and get me, coppers moments.