Question

I would like a simple way to get yesterday’s date (local time) as a string in a Perl script. Preferably, I would like to do this with no module dependencies, since we have a bare bones Perl 5.12 installation.

So, something like:

my $yesterdays_date=...; # Puts for example '301011' into $yesterdays_date, 
                         # if today is October 31st, 2011

Answer 1

Time::Piece is core:

use Time::Piece;
use Time::Seconds qw(ONE_DAY);

my $yesterday = localtime() - ONE_DAY();
print $yesterday->strftime('%d%m%y'), "\n";

If you’re concerned about daylight savings, you can normalize the current time to near noon:

use Time::Piece;
use Time::Seconds qw(ONE_DAY ONE_HOUR);

my $today = localtime;
my $yesterday = $today + ONE_HOUR * ( 12 - $today->hour ) - ONE_DAY;
print $yesterday->strftime("%d%m%y"), "\n";

If you can live with dependencies, then use DateTime:

use DateTime;

print DateTime->now->subtract(days => 1)->strftime('%d%m%y'), "\n";