Re: How to subtract date by 1 day

[Zaxo]

Subtract 24*60*60 seconds from the unix time before using localtime to split into units.

I recommend POSIX::strftime for converting that to a string.

use POSIX 'strftime';
print strftime "%Y_%m_%d_%H_%M_%S/n", localtime() - 24 * 60 * 60;

prints this time yesterday in your format.

[ikegami]

If by day, the OP means 24 hours, that's fine. If he just wants to move back the date one day without changing the time, your solution is wrong since not every day has 24*60*60 seconds. Use timegm+gmtime to do date manips.

use POSIX       qw( strftime );
use Time::Local qw( timegm );

my ($d,$m,$y) = (localtime())[3,4,5];

print(strftime("%Y_%m_%d\n", 
   gmtime(timegm(0,0,0,$d,$m,$y) - 24*60*60)
));

With time:

use POSIX       qw( strftime );
use Time::Local qw( timegm );

my ($sec,$min,$hour,$d,$m,$y) = localtime();
($d,$m,$y) = (gmtime(timegm(0,0,0,$d,$m,$y) - 24*60*60))[3,4,5];

print(strftime("%Y_%m_%d_%H_%M_%S\n", $sec,$min,$hour,$d,$m,$y));