How to iterate through range of Dates? - windows

Question

In my script, I need to iterate through a range of dates given the start date and end date. How can I do this in Perl?

Answer 1

Use DateTime module. Here is a simple example which lists the ten previous days:
use 5.012;
use warnings;
use DateTime;
my $end = DateTime->now;
my $day = $end->clone->subtract( days => 10 ); # ten days ago
while ($day < $end) {
say $day;
$day->add( days => 1 ); # move along to next day
}
Update (after seeing your comment/update):
To parse in a date string then look at the DateTime::Format on modules CPAN.
Here is an example using DateTime::Format::DateParse which does parse YYYY/MM/DD:
use DateTime::Format::DateParse;
my $d = DateTime::Format::DateParse->parse_datetime( '2010/06/23' );

Answer 2

One easy approach is to use the Date::Simple module, which makes use of operator-overloading:
use strict;
use warnings;
use Date::Simple;
my $date = Date::Simple->new ( '2010-01-01' ); # Stores Date::Simple object
my $endDate = Date::Simple->today; # Today's date
while ( ++$date < $endDate ) {
print ( $date - $endDate ) , "day",
( ( $date-$endDate) == 1 ? '' : 's' ), " ago\n";
}

Answer 3

use DateTime::Format::Strptime qw();
my $start = DateTime::Format::Strptime->new(pattern => '%Y/%m/%d')->parse_datetime('2010/08/16');
my $end = DateTime::Format::Strptime->new(pattern => '%Y/%m/%d')->parse_datetime('2010/11/24');
while ($start < $end) {
$start->add(days => 1);
say $start->ymd('/');
}

Answer 4

I like to use the fact that strftime will normalize the date for me:
#!/usr/bin/perl
use strict;
use warnings;
use POSIX qw/strftime/;
my $start = "2010/08/16";
my $end = "2010/09/16";
my #time = (0, 0, 0);
my ($y, $m, $d) = split "/", $start;
$y -= 1900;
$m--;
my $offset = 0;
while ((my $date = strftime "%Y/%m/%d", #time, $d + $offset, $m, $y) le $end) {
print "$date\n";
} continue {
$offset++;
}

Answer 5

You can try Date::Calc::Iterator
# This puts all the dates from Dec 1, 2003 to Dec 10, 2003 in #dates1
# #dates1 will contain ([2003,12,1],[2003,12,2] ... [2003,12,10]) ;
my $i1 = Date::Calc::Iterator->new(from => [2003,12,1], to => [2003,12,10]) ;
my #dates1 ;
push #dates1,$_ while $_ = $i1->next ;

Answer 6

If installing extra perl modules is not preferable, one can use this approach, based on a core perl library POSIX:
#!/usr/bin/perl
use strict;
use warnings;
use POSIX qw(strftime);
# CREATE CALENDAR
my #Calendar = ();
my $years = 3;
my #Now = localtime(); # An array of 9 date-time parameters.
for my $count ( 0 .. ( 365 * $years ) ) {
# If date is January 1st, manual shift to December 31st is needed,
# because days ([yday][2]) are counted from January 31st and never shift back one year.
if( $Now[4] == 0 && $Now[3] == 1 ) {
unshift #Calendar, strftime( "%Y-%m-%d", #Now );
$Now[5] --; # Reduce by one the sixth array element #5 - year.
$Now[4] = 11; # Set fifth array element № 4 - to December.
$Now[3] = 31; # Set fourth array element № 3 - to 31st.
} else {
unshift #Calendar, strftime( "%Y-%m-%d", #Now );
$Now[3] --;
}
}
# Print out.
my $size = #Calendar;
for (my $i = 0; $i < $size; $i++) {
print $Calendar[$i]."\n";
}

Answer 7

Perl has a rich array of time and date manipulation modules, as seen here:
http://datetime.perl.org/?Modules
And there are some examples of date and time problems there as well.
With Perl, there's always more than one way to do it.