Yes. Set $Data::Dumper::Freezer to the name of the method you want called, then implement that method in DateTime, e.g.

$Data::Dumper::Freezer = 'my_dumper';

sub DateTime::my_dumper { ... }
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Even better, you can localize the change to $Data::Dumper::Freezer so pretty-printing only happens when you want it to.

EDIT: Corrected to DateTime::my_dumper...