Getting Date - Adding and Subtracting

use DateTime;

my $dt1 = DateTime-> new (
            year =>'1998',
            month =>'4',
            day   =>'4',
            hour  =>'21',
            time_zone =>'local'
            );

my $Tomorrow = $dt1->add( days => 1 )

my $Yesterday = $dt1->subtract( days => 1 );

* You can also change date time by hour or seconds.