P
PerlFAQ Server
This is an excerpt from the latest version perlfaq4.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .
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4.17: How do I find yesterday's date?
(contributed by brian d foy)
Use one of the Date modules. The "DateTime" module makes it simple, and
give you the same time of day, only the day before.
use DateTime;
my $yesterday = DateTime->now->subtract( days => 1 );
print "Yesterday was $yesterday\n";
You can also use the "Date::Calc" module using its "Today_and_Now"
function.
use Date::Calc qw( Today_and_Now Add_Delta_DHMS );
my @date_time = Add_Delta_DHMS( Today_and_Now(), -1, 0, 0, 0 );
print "@date_time\n";
Most people try to use the time rather than the calendar to figure out
dates, but that assumes that days are twenty-four hours each. For most
people, there are two days a year when they aren't: the switch to and
from summer time throws this off. Let the modules do the work.
If you absolutely must do it yourself (or can't use one of the modules),
here's a solution using "Time::Local", which comes with Perl:
# contributed by Gunnar Hjalmarsson
use Time::Local;
my $today = timelocal 0, 0, 12, ( localtime )[3..5];
my ($d, $m, $y) = ( localtime $today-86400 )[3..5];
printf "Yesterday: %d-%02d-%02d\n", $y+1900, $m+1, $d;
In this case, you measure the day starting at noon, and subtract 24
hours. Even if the length of the calendar day is 23 or 25 hours, you'll
still end up on the previous calendar day, although not at noon. Since
you don't care about the time, the one hour difference doesn't matter
and you end up with the previous date.
--------------------------------------------------------------------
The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.
If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .
--------------------------------------------------------------------
4.17: How do I find yesterday's date?
(contributed by brian d foy)
Use one of the Date modules. The "DateTime" module makes it simple, and
give you the same time of day, only the day before.
use DateTime;
my $yesterday = DateTime->now->subtract( days => 1 );
print "Yesterday was $yesterday\n";
You can also use the "Date::Calc" module using its "Today_and_Now"
function.
use Date::Calc qw( Today_and_Now Add_Delta_DHMS );
my @date_time = Add_Delta_DHMS( Today_and_Now(), -1, 0, 0, 0 );
print "@date_time\n";
Most people try to use the time rather than the calendar to figure out
dates, but that assumes that days are twenty-four hours each. For most
people, there are two days a year when they aren't: the switch to and
from summer time throws this off. Let the modules do the work.
If you absolutely must do it yourself (or can't use one of the modules),
here's a solution using "Time::Local", which comes with Perl:
# contributed by Gunnar Hjalmarsson
use Time::Local;
my $today = timelocal 0, 0, 12, ( localtime )[3..5];
my ($d, $m, $y) = ( localtime $today-86400 )[3..5];
printf "Yesterday: %d-%02d-%02d\n", $y+1900, $m+1, $d;
In this case, you measure the day starting at noon, and subtract 24
hours. Even if the length of the calendar day is 23 or 25 hours, you'll
still end up on the previous calendar day, although not at noon. Since
you don't care about the time, the one hour difference doesn't matter
and you end up with the previous date.
--------------------------------------------------------------------
The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.
If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.