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Comparing two dates and getting back difference in days

by TASdvlper (Monk)
on Jan 21, 2004 at 16:28 UTC ( #322933=perlquestion: print w/ replies, xml ) Need Help??
TASdvlper has asked for the wisdom of the Perl Monks concerning the following question:

Hello all, I have two dates, in the format YYYY-MM-DD, say ...
use Date::Manip; my $date1 = "2004-01-14" my $date2 = UnixDate(ParseDate("today"),"%Y-%m-%d");
I'm trying to use Date_Cmp($date1, $date2) to get the difference in days (I don't care about hours, minutes, seconds, ..) but I keep getting back "1" as the result. Am I doing something wrong ?

I've also read that Date::Manip is a very big and slow module. Is there a better one to use for this type of calculation ?

As always, thanks in advance.

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Re: Comparing two dates and getting back difference in days
by Roy Johnson (Monsignor) on Jan 21, 2004 at 16:34 UTC
    How about the Delta_Days function in Date::Calc? Date_Cmp is just like cmp, returning +1, 0, or -1 to indicate greater than, equal, or less than.

    The PerlMonk tr/// Advocate
Re: Comparing two dates and getting back difference in days
by jdtoronto (Prior) on Jan 21, 2004 at 16:35 UTC
    Try Time::Piece. I discovered it a few days back and it is mucho-small, very fast and does the basic comparisons. It has relatives Time::Piece::MySQL for MySQL date/time types and when you do a calculation it returns a Time::Seconds object. Very nice little bundle.

    I also use Date::Manip, but it is too big and heavy for this sort of lifting!

    jdtoronto

Re: Comparing two dates and getting back difference in days
by duff (Vicar) on Jan 21, 2004 at 16:38 UTC

    There's always good old Time::Local and hand parsing (untested):

    #!/usr/bin/perl use Time::Local; my $now_gmt = time; my $then = "2004-01-14"; my ($ty,$tm,$td) = $then =~ /^(\d\d\d\d)-(\d\d)-(\d\d)$/; my $then_gmt = timegm(0,0,0,$td,$tm-1,$ty); my $diff_in_days = int(($now_gmt - $then_gmt) / 86400);
Re: Comparing two dates and getting back difference in days
by Aragorn (Curate) on Jan 21, 2004 at 16:38 UTC
    Date_Cmp just returns if $date1 is smaller than, equal to, or greater than $date2, like the Perl cmp operator.

    What you want to do can be done with the DateCalc function. See the documentation of Date::Manip for details.

    The Date::Calc module is implemented mostly in C and should be a lot faster.

    Arjen

      Ok, I'm looking at DateCalc but I can't seem to figure out how to get the output in just days. I'm getting output that looks like this:
      2004-01-14 2004-01-21 +0:0:1:0:0:0:0
      Do I have to do my own conversion to just days ? Also, I could seem to figure out what the $err was supposed to be.
Re: Comparing two dates and getting back difference in days
by Limbic~Region (Chancellor) on Jan 21, 2004 at 17:01 UTC
    TASdvlper,
    Here is a TIMTOWTDI solution. The Seconds2English module you will not find on CPAN as I wrote for learning purposes. I have actually refined it quite a bit, but unfortunately that code is unavailable at the moment.
    #!/usr/bin/perl -w use strict; use Time::Local; use Seconds2English; my $date1 = epoch('2004-01-14'); my $date2 = epoch('2003-12-25'); my $diff = Seconds2English->new('start' => $date2 - $date1); print "The difference is " , $diff->in_days, " days\n"; sub epoch { my ($year, $month, $day) = split '-' , shift; return timelocal(0 , 0 , 12, $day , $month - 1, $year); } __END__ The difference is 20 days
    Cheers - L~R
Re: Comparing two dates and getting back difference in days
by Anonymous Monk on Jan 21, 2004 at 17:23 UTC
    Date::Simple does a nice job for simple calculations.

    Chris

    #!/usr/bin/perl use strict; use warnings; use Date::Simple; my $date1 = Date::Simple->new("2004-01-14"); my $date2 = Date::Simple->new("2004-01-17"); print "Days difference is: ", $date2 - $date1, "\n";
Re: Comparing two dates and getting back difference in days
by flyingmoose (Priest) on Jan 21, 2004 at 17:24 UTC
    So many Date and Time modules to try, so little time :)
      That's how it used to be before DateTime. That's why there is only DateTime now.
      use DateTime; use strict; use warnings; my $str = "2004-01-14"; my( $y, $m, $d ) = split /\D/,$str; my $delta = DateTime->new( year => $y, month => $m, day => $d, )->delta_days( DateTime->now(), ); die $delta->days; __END__ 0 at datetime4.pl line 16.
        DateTime homepage

        Is there an ActiveState repository with it?


        The PerlMonk tr/// Advocate
Re: Comparing two dates and getting back difference in days
by phydeauxarff (Priest) on Jan 21, 2004 at 17:37 UTC
    Throwing in one more thing to consider when comparing dates...

    I use date::business because I typically need to figure out how many "business days" have passed and this module does a good job of not only figuring the weekdays, but also allows you to skip holidays.

    using the diffb() function in this module will count the number of days between a Friday and a Monday as 1.

Re: Comparing two dates and getting back difference in days
by BrowserUk (Pope) on Jan 21, 2004 at 18:23 UTC

      If you look at the rest of the nodes that I have written you will discover that I am a big Date::Manip fan.

      That been said, I think that "slow" is a relative term. Yes it is big, but when ever I have implimented it into my scripts, I have found very little, if any, time lag. If you are trying to scrape every last clock cycle out of a huge script, you probably don't want to use it. But if a milli-second or so doesn't matter to you, the flexibility of Date::Manip makes it more than worth it. I can honestly say that I haven't used any of the other Date conversion modules, mainly because Date::Manip has everything that I need. I guess once you get to know a module, you kind of get stuck on it. Mind you that I am not knocking any of the other modules, I just think that for what you get out of it, Date::Manip is where it's at.

      Paulster2

Re: Comparing two dates and getting back difference in days
by injunjoel (Priest) on Jan 22, 2004 at 18:30 UTC
    Greetings all,
    A little late I know but here is what I use for small cases.
    #!/usr/bin/perl -w use strict; use Time::Local; my $start_date_str = "2004-01-14";#date you are testing; my ($year,$month,$day) = split(/\-/,$start_date_str); $month--;#timelocal months are 0-11; my $start_seconds = timelocal(0,0,0,$day, $month, $year); my $today_seconds = time(); my $days_between = ( int( ( ( (abs($start_seconds - $today_seconds))/6 +0 )/60 )/24 ) ); print $days_between; exit;
    Previewing it I must admit its not very elegant, but it works for me.
    Hope that helps get you part of the way there.

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