Counting days with DateTime

htmanning has asked for the wisdom of the Perl Monks concerning the following question:

Monks, I'm doing a simple reservation system and using DateTime I can make sure the reservation is not before today.

use DateTime;
    my $now = DateTime->now( time_zone => 'Pacific/Honolulu' );
    my $reservation_date = DateTime->new(
        year    => $CONFIG{'date_year'},
        month   => $CONFIG{'date_month'},
        day     => $CONFIG{'date_day'},
        hour    => $myhour,
        minute  => $mymin,
        time_zone  => 'Pacific/Honolulu',
    );
    

if ($reservation_date < $now) {
print "error";
}
[download]

But what I need now is to restrict future reservations to no more than 1 week ahead of time, but something like this doesn't work:

} elsif ($reservation_date - $now > 7) {
do something.
}
[download]

It seems I have to use the duration compare class, but I'm not sure how to do it when I'm only comparing the reservation date to now, and the base time to compare to is now.

Comment on Counting days with DateTime Select or Download Code

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Re: Counting days with DateTime (updated x2) by haukex (Archbishop) on Apr 01, 2020 at 19:06 UTC
Personally I try to avoid the overloaded DateTime math operators, and only use the comparisons. I'd suggest something like: `my $now = DateTime->now( time_zone => 'Pacific/Honolulu' ); my $one_week_from_now = $now->clone->add( weeks=>1 ); if ( $reservation_date > $one_week_from_now ) ...` [download] Update: Corrected `->add( week=>1 )` to `->add( weeks=>1 )`! Update 2: Added `->clone`, as suggested by tobyink below. That's what I get for running a different test case (`DateTime->now->add(weeks=>1)`) than what I posted here `:-/`	[reply] [d/l] [select]
Re^2: Counting days with DateTime (updated) by tobyink (Canon) on Apr 02, 2020 at 07:18 UTC
Consider using: `my $one_week_from_now = $now->clone->add( weeks=>1 );` [download] This is because most of the DateTime add/subtract methods mutate the object the operated on, and you probably don't want `$now` to be a date in the future! toby döt ink	[reply] [d/l] [select]
Re^2: Counting days with DateTime by htmanning (Friar) on Apr 01, 2020 at 19:33 UTC
Thanks so much! This worked after I changed "week" to "weeks."	[reply]
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Re: Counting days with DateTime by Corion (Patriarch) on Apr 01, 2020 at 18:54 UTC
DateTime is very finnicky with differences and timezones, but as you're using the same timezone in both elements, maybe you just need the `->delta_days` method?	[reply] [d/l]
Re: Counting days with DateTime by soonix (Chancellor) on Apr 02, 2020 at 08:36 UTC
The duration class is DateTime's way to specify whether your '7' stands for '7 seconds' (as it would be in unix time stamps), or '7 days', '7 years', or other units in between. You'd have to write `DateTime::Duration->new( days => 7 )` [download] or, since in the text you you wrote "1 week", not "7 days": `DateTime::Duration->new( weeks => 1 )` [download] instead of that simple 7.	[reply] [d/l] [select]