gistfile1.txt

use Red;

model ModX is rw {
    has UInt $.id is serial;
    has DateTime $.dt is column{ :nullable };
}

red-defaults('Pg',
host => Str,
dbname => "rcb_dev",
user => "patrickb"
);
#red-defaults "SQLite";
#ModX.^create-table;

my ModX $x = ModX.^create: dt => DateTime.now;

$x.dt = Nil;
$x.^save;

gistfile2.txt

Invocant of method 'utc' must be an object instance of type 'DateTime',
not a type object of type 'DateTime'.  Did you forget a '.new'?
  in method deflate at /home/patrickb/repos/RakudoCIBot/../Red/lib/Red/Driver/Pg.pm6 (Red::Driver::Pg) line 218
  in block  at /home/patrickb/repos/RakudoCIBot/../Red/lib/Red/Driver.pm6 (Red::Driver) line 88
  in block  at /home/patrickb/repos/RakudoCIBot/../Red/lib/Red/Driver.pm6 (Red::Driver) line 85
  in method prepare at /home/patrickb/repos/RakudoCIBot/../Red/lib/Red/Driver.pm6 (Red::Driver) line 82
  in method execute at /home/patrickb/repos/RakudoCIBot/../Red/lib/Red/Driver.pm6 (Red::Driver) line 116
  in method save at /home/patrickb/repos/Red/lib/MetamodelX/Red/Model.pm6 (MetamodelX::Red::Model) line 451
  in method save at /home/patrickb/repos/Red/lib/MetamodelX/Red/Model.pm6 (MetamodelX::Red::Model) line 469
  in block <unit> at foo.raku line 19

gistfile3.txt

This is what I get when using SQLite:

Use of uninitialized value of type DateTime in string context.
Methods .^name, .raku, .gist, or .say can be used to stringify it to something meaningful.
  in method deflate at /home/patrickb/repos/RakudoCIBot/../Red/lib/Red/Driver/CommonSQL.pm6 (Red::Driver::CommonSQL) line 884