Ga Mmeeu Ga Mmeeu - 5 months ago 12
Perl Question

Perl: Calculate number of days by converting to seconds

I am trying to calculate the number of calendar days between two dates extracted from a database. I thought that converting the dates to seconds would be a simple and correct solution.

#!/usr/bin/perl
use warnings;
use strict;
use POSIX qw(strftime);
use Date::Parse;

my $minDate = "2016-03-27";
my $maxDate = "2016-06-15";

print "Format as extracted from db: mindate: $minDate and maxdate: $maxDate\n";

my ($dbYear,$dbMonth,$dbDay) = split ('-', $minDate);
my $datum = "$dbYear$dbMonth$dbDay";
my $minDateSec = str2time($datum);

($dbYear,$dbMonth,$dbDay) = split ('-', $maxDate);
$datum = "$dbYear$dbMonth$dbDay";
my $maxDateSec = str2time($datum);

my $numCalDaysSec = ($maxDateSec-$minDateSec)/86400;

print "Min date in Seconds: $minDateSec\n";
print "Max date in Seconds: $maxDateSec\n";
print "Num days: $numCalDaysSec\n";


Initially, I thought that this method provided me with reliable results:

bash-3.2$ ./testNumDays.pl
As extracted from db: mindate: 2016-06-14 and maxdate: 2016-06-15
Min date in Seconds: 1465855200
Max date in Seconds: 1465941600
Num days: 1
bash-3.2$ ./testNumDays.pl
As extracted from db: mindate: 2016-05-31 and maxdate: 2016-06-15
Min date in Seconds: 1464645600
Max date in Seconds: 1465941600
Num days: 15
bash-3.2$ ./testNumDays.pl
As extracted from db: mindate: 2016-03-28 and maxdate: 2016-06-15
Min date in Seconds: 1459116000
Max date in Seconds: 1465941600
Num days: 79
bash-3.2$ ./testNumDays.pl
As extracted from db: mindate: 2016-03-27 and maxdate: 2016-06-15
Min date in Seconds: 1459033200
Max date in Seconds: 1465941600
Num days: 79.9583333333333
bash-3.2$


Obviously, the number of calendar dates between dates should be an integer. Mmmm, what I am doing wrong? Why is converting to seconds not reliable?

Since I am a Perl newbie, I am probably overlooking the obvious. Any help is therefore more than welcome.

Answer

One way is to use the Time::Piece Core module:

use warnings;
use strict;
use Time::Piece qw();

my $t1 = Time::Piece->strptime('2016-03-27', '%Y-%m-%d');
my $t2 = Time::Piece->strptime('2016-06-15', '%Y-%m-%d');
my $seconds = $t2 - $t1;
print $seconds->days(), "\n";

__END__

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