use warnings;
use strict;

my $tot = 0;
while (<DATA>) {
    my ($num, $date) = split;
    $tot += $num;
    printf "%-5d %s\n", $tot, $date;
}

__DATA__
1   2005-01-16
6   2005-01-28
1   2005-01-31
2   2005-02-01
2   2005-02-02
1   2005-02-05