List of days between start and end dates - perl

Question

Im trying to get each individual date between a start and an end date in Perl. I had initially done it for 7 days using the code below :
use Time::ParseDate;
my $newdate;
my $newtime;
my #dates = ();
my $newtime->[0] = parsedate($start_datetime);
my $newdate->[0] = strftime("%Y-%m-%d",localtime($newtime->[0]));
push(#dates, $newdate->[0]);
my $newtime->[1] = parsedate($newdate->[0]) + (1 * 24 * 60 * 60);
my $newdate->[1] = strftime("%Y-%m-%d",localtime($newtime->[1]));
push(#dates, $newdate->[1]);
my $newtime->[2] = parsedate($newdate->[1]) + (1 * 24 * 60 * 60);
my $newdate->[2] = strftime("%Y-%m-%d",localtime($newtime->[2]));
push(#dates, $newdate->[2]);
my $newtime->[3] = parsedate($newdate->[2]) + (1 * 24 * 60 * 60);
my $newdate->[3] = strftime("%Y-%m-%d",localtime($newtime->[3]));
push(#dates, $newdate->[3]);
my $newtime->[4] = parsedate($newdate->[3]) + (1 * 24 * 60 * 60);
my $newdate->[4] = strftime("%Y-%m-%d",localtime($newtime->[4]));
push(#dates, $newdate->[4]);
my $newtime->[5] = parsedate($newdate->[4]) + (1 * 24 * 60 * 60);
my $newdate->[5] = strftime("%Y-%m-%d",localtime($newtime->[5]));
push(#dates, $newdate->[5]);
my $newtime->[6] = parsedate($newdate->[5]) + (1 * 24 * 60 * 60);
my $newdate->[6] = strftime("%Y-%m-%d",localtime($newtime->[6]));
push(#dates, $newdate->[6]);
my $newtime->[7] = parsedate($newdate->[6]) + (1 * 24 * 60 * 60);
my $newdate->[7] = strftime("%Y-%m-%d",localtime($newtime->[7]));
push(#dates, $newdate->[7]);
but realized that it should be able to work for any number of days.
so I tried the loop below but it didnt quite work for me
my $newdate;
my $newtime;
my #dates = ();
my $start_date = substr($start_datetime, 0, 10) ;
$start_date =~ s/-//gi;
my $end_date = substr($end_datetime, 0, 10) ;
$end_date =~ s/-//gi;
my $days = yyyymmdd_to_rata_die($end_date) - yyyymmdd_to_rata_die($start_date);
my $newtime->[0] = parsedate($xml->{action_content}->{start_date});
my $newdate->[0] = strftime("%Y-%m-%d",localtime($newtime->[0]));
push(#dates, $newdate->[0]);
for(my $x=1;$x<$days;$x++)
{
my $newtime->[$x] = parsedate($newdate->[$x-1]) + (1 * 24 * 60 * 60);
my $newdate->[$x] = strftime("%Y-%m-%d",localtime($newtime->[$x]));
push(#dates, $newdate->[$x]);
}
I got the function below from a question here on Stackoverflow
sub yyyymmdd_to_rata_die
{
use integer;
my ( $y, $m, $d ) = $_[0] =~ /\A([0-9]{4})([0-9]{2})([0-9]{2})\z/
or return;
my $adj;
if ( $m <= 2 )
{
$y -= ( $adj = ( 14 - $m ) / 12 );
$m += 12 * $adj;
}
elsif ( $m > 14 )
{
$y += ( $adj = ( $m - 3 ) / 12 );
$m -= 12 * $adj;
}
$d += ( $m * 367 - 1094 ) / 12 + $y % 100 * 1461 / 4 + ( $y / 100 * 36524 + $y / 400 ) - 306;
}
any assistance will be greatly apreciated
EDIT:
$start_datetime = "2014-09-01 00:00:00";
$end_datetime = "2014-09-07 23:59:59";
I need all the days in between the start and end date ie.
2014-09-01
2014-09-02
2014-09-03
2014-09-04
2014-09-05
2014-09-06
2014-09-07

Answer 1

I recommend that you use the Time::Piece module. It shouldn't need installing as it has been a core module since version 10 of Perl 5.
It would look like this
use strict;
use warnings;
use Time::Piece;
print days_between('2014-01-01', '2014-12-01'), "\n";
sub days_between {
my ($start, $end) = map Time::Piece->strptime($_, '%Y-%m-%d'), #_;
($end - $start)->days;
}
output
334
Update
I apologize. I misunderstood your requirements and thought you wanted the number of days between the two dates. This program prints a list of all the dates between and including the two limits. If called in scalar context it will provide the number of days in the list, as before.
use strict;
use warnings;
use Time::Piece;
use Time::Seconds qw/ ONE_DAY /;
printf "%d days:\n", scalar days_from_to('2014-09-01 00:00:00', '2014-09-07 23:59:59');
print "$_\n" for days_from_to('2014-09-01 00:00:00', '2014-09-07 23:59:59');
sub days_from_to {
my #limits = map /(\d\d\d\d-\d\d-\d\d)/, #_;
#limits = map Time::Piece->strptime($_, '%Y-%m-%d'), #limits;
my #dates = ( $limits[0] );
push #dates, $dates[-1] + ONE_DAY while $dates[-1] < $limits[-1];
map $_->ymd, #dates;
}
output
7 days:
2014-09-01
2014-09-02
2014-09-03
2014-09-04
2014-09-05
2014-09-06
2014-09-07
Update
If a more critical regex is required that will reject strings like 0123-45-67 then you can use this
my $date_re = qr/(?:
(?: (?:19|20)[0-9][0-9] ) -
(?:
(?: 0?[469] | 11 ) -
(?: 0?[1-9] | [12][0-9] | 30 )
|
(?: 0?[13578] | 1[02] ) -
(?: 0?[1-9] | [12][0-9] | 3[01] )
|
(?: 0?2 ) -
(?: 0?[1-9] | [12][0-9] )
)
)/x;
which will accept dates between 1900 and 2099, and makes sure that the day of the month is valid for that month. The only proviso is that it will allow 29 February in any year.
Or you may prefer to use Regexp::Common::time like this
use Regexp::Common qw/ time /;
my $date_re = $RE{time}{strftime}{-pat => '%Y-%m-%d'};
but this has the same issue with 29 February.
The subroutine will look like this
sub days_from_to {
my #limits = map /($date_re)/, #_;
#limits = map Time::Piece->strptime($_, '%Y-%m-%d'), #limits;
my #dates = ( $limits[0] );
push #dates, $dates[-1] + ONE_DAY while $dates[-1] < $limits[-1];
map $_->ymd, #dates;
}

Answer 2

You can make your life a lot easier by using something like Time::Piece;
#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
use Time::Piece;
use Time::Seconds;
my $fmt = '%Y-%m-%d';
my $start_date = '2014-09-08';
my $days = 30;
my #dates;
my $date = Time::Piece->strptime($start_date, $fmt);
foreach (1 .. $days) {
push #dates, $date;
$date += ONE_DAY;
}
say $_ for #dates;
Update: Looks like Borodin's answer uses a very similar approach and deals with the inputs and required outputs that you have added to your question.