Compute NUM of days from UNION of time ranges (with DateTime::Span) - perl

Question

I have a set of time ranges and need to get the Number of days from this set. I did it with DateTime::Span as follows:
use DateTime;
use DateTime::Span;
sub printHash {
my $hash = shift;
foreach my $key (keys %{$hash}) {
print "$key: $hash->{$key}\n";
}
}
$date1 = DateTime->new( year => 2002, month => 3, day => 11 );
$date2 = DateTime->new( year => 2002, month => 4, day => 12 );
$date3 = DateTime->new( year => 2003, month => 8, day => 26 );
$date4 = DateTime->new( year => 2003, month => 9, day => 15 );
$date5 = DateTime->new( year => 2004, month => 7, day => 6 );
$date6 = DateTime->new( year => 2004, month => 10, day => 15 );
$set1 = DateTime::Span->from_datetimes( start => $date1, end => $date2 );
$set2 = DateTime::Span->from_datetimes( start => $date3, end => $date4 );
$set3 = DateTime::Span->from_datetimes( start => $date5, end => $date6 );
$set123 = $set1->union( $set2, $set3 );
printHash(\%$set123);
#--------------------------------
set123:
set: [2002-03-11T00:00:00..2002-04-12T00:00:00],[2003-08-26T00:00:00..2003-09
T00:00:00],[2004-07-06T00:00:00..2004-10-15T00:00:00]
Is there a way to extract the Number of days in this $set123? Thanks a lot!
Update: I can do it with delta_days but it's actually I do need a UNION of the time ranges then find the Number of days within this UNION set. I find DateTime::Span works well to find the UNION but I just need to know how to extract the Number of days in it. Since I need a solution in a hurry, so please help! Thanks!

Answer 1

First, you're calling union incorrectly. It only takes one argument.
$set1->union($set2)->union($set3);
Secondly, the result of a union is actually a DateTime::SpanSet, not a DateTime::Span.
my $spanset = $set1->union($set2)->union($set3);
Finally, both ::Span and ::SpanSet provide a method called duration which return a DateTime::Duration object.
my $dur = $spanset->duration();
Unfortunately, it doesn't return the result as days, and it's impossible to convert what it does return into days. That means you need to iterate over the spans that make up the span set, and sum the size of those.
my $days = 0;
my $iter = $spanset->iterator();
while ( my $span = $iter->next ) {
my $date1 = $span->start;
my $date2 = $span->end;
$days += $date2->delta_days($date1)->in_units('days');
}
print("$days\n"); # 153

Answer 2

Actually, you don't need to use DateTime::Span. The delta_days method of DateTime does the trick nicely:
use strict;
use warnings;
use DateTime;
my $dt1=DateTime->new(year=>2002,month=>3,day=>11,time_zone=>"local");
my $dt2=DateTime->new(year=>2002,month=>4,day=>11,time_zone=>"local");
print $dt2->delta_days($dt1)->in_units("days") . "\n"; #31