Without seeing the actual code I can't help you with the details, but the general idea is correct:

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use enum qw( DATE TIME );

my @reservations = ([ '2020-03-21', '2:00 pm' ],
                    [ '2020-03-21', '3:00 pm' ],
                    [ '2020-03-22', '2:00:pm' ]);

my $last_date = "";
for my $reservation (@reservations) {
    print $last_date eq $reservation->[DATE] ? ' ' x 10 : $reservation
+->[DATE];
    say ' ', $reservation->[TIME];
    $last_date = $reservation->[DATE];
}
[download]

Output:

2020-03-21 2:00 pm
           3:00 pm
2020-03-22 2:00:pm
[download]