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help on getting date

by Anonymous Monk
on Jun 02, 2003 at 16:14 UTC ( #262412=perlquestion: print w/ replies, xml ) Need Help??
Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hello everyone , Is there a way to get the system date using perl in the following format mm-dd-yyyy , and then is there a way to compare the dates to see which is greater or lesser then a given date which is also in mm-dd-yyyy format Thank you for your help

Comment on help on getting date
Re: help on getting date
by hardburn (Abbot) on Jun 02, 2003 at 16:17 UTC

    You can get dates using localtime.

    Comparing dates is trickier. Dig through the Date:: and DateTime:: modules. The DateTime:: namespace is for a new project trying to unify Perl's mess of Date and Time modules into a single, consistant API, so look there first.

    ----
    I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
    -- Schemer

    Note: All code is untested, unless otherwise stated

Re: help on getting date
by halley (Prior) on Jun 02, 2003 at 16:20 UTC

    Personally, if sorting or comparing human-readable dates is important, I'd recommend YYYY-MM-DD format. It naturally sorts, and reduces ordering confusion about 3 June or 6 January. Bigger units to the left.

    As mentioned, localtime() will return the individual components for you. Just remember to add 1 to the month and 1900 to the year.

    If your data is already IN the poor MM-DD-YYYY format, then you'll need the help of one of the Date::* modules to convert or compute back to a useful scalar unit like epoch time, Julian dates, or something. Keep dates numeric internally, and provide formatted equivalents only for user presentation.

    --
    [ e d @ h a l l e y . c c ]

      First off I want to emphasize that you're right on all the really important points. The nit I will pick is that "need" is kind of a strong word, given that there's a pretty simple way to convert MM-DD-YYYY to YYYY-MM-DD format, even if it's not widely capable like a Date::* module:

      # assumes you have 0-padded dates, but if you don't you can change # the \d\d's to \d\d?'s , and do an appropriate sprintf. my @ymd = map { my ($m, $d, $y) = $_ =~ /(\d\d)-(\d\d)-(\d{4})/; "$y- +$m-$d"; } @dmy;

      HTH

      If not P, what? Q maybe?
      "Sidney Morgenbesser"

        why bother with the temporary variables, especially inside map? Heck, you'd also screen out a small subset of invalid data.
        print  map {$_ =~ /(\d\d)-(\d\d)-(\d{4})/ && "$3-$1-$2"; } ("01-02-1999");
        of course, using this kind of code, you'd need to make sure that your dataset's valid -- you won't get Date::Manip's heavy duty "Am I valid datetime or not" routines.

Re: help on getting date
by Mr. Muskrat (Abbot) on Jun 02, 2003 at 16:20 UTC

    Take a look at Date::Calc for working with dates. The documentation for it has a recipe for comparing dates.

    As far as formatting to mm-dd-yy, you can use printf or sprintf to do that depending on what you want to do with it once it is formatted.

•Re: help on getting date
by merlyn (Sage) on Jun 02, 2003 at 16:29 UTC

      The comment is totally inappropriate. I had considered making it myself.

      Cheers,
      Ovid

      New address of my CGI Course.
      Silence is Evil (feel free to copy and distribute widely - note copyright text)

        That makes three of us.. :) And since there are obviously quite a few who thought the same I say we leave it here so the rest of us can move on. (I'm sure merlyn will be glad to stand-in for us in taking the heat for actually making the comment.. ;-) SCNR..)

        Makeshifts last the longest.

Re: help on getting date
by fglock (Vicar) on Jun 02, 2003 at 17:00 UTC
    my $dt = DateTime->now; print "system date ", $dt->strftime( "%m-%d-%Y" ); my $compare = $dt <=> $other_date;

    Note: $other_date must be a DateTime object

Re: help on getting date
by fglock (Vicar) on Jun 02, 2003 at 17:26 UTC

    You can use DateTime::Format::Strptime

    use DateTime::Format::Strptime; my $pat = DateTime::Format::Strptime->new( pattern => '%m-%d-%Y' ); my $dt1 = $pat->parse_datetime( "06-07-2003" ); my $dt2 = $pat->parse_datetime( "07-06-2003" ); print $dt1 < $dt2 ? "smaller" : "equal or bigger";
Re: help on getting date
by crouchingpenguin (Priest) on Jun 02, 2003 at 18:23 UTC

    1. Is there a way to get the system date using perl in the following format mm-dd-yyyy?

    Yes, using POSIX::strftime:

    print POSIX::strftime("%m-%d-%Y",localtime()),"\n";

    2. is there a way to compare the dates to see which is greater or lesser then a given date which is in mm-dd-yyyy format?

    Yes, using POSIX::mktime() and optionally POSIX::difftime():

    my $start_date_string = '05-03-2003'; my @date_parts = split('-',$start_date_string); # build time my $then_time = POSIX::mktime( 0,0,0, $date_parts[1], ($date_parts[0] -1), ($date_parts[2] - 1900) ); ### or could be mktime() from another split string here my $now_time = time(); #could also use POSIX::difftime: #"the time difference (in seconds) between two times #(as returned by 'time()')" if( $then_time < $now_time ){ print POSIX::ctime($then_time) . " was before " . POSIX::ctime($now_time) . "\n"; }else{ print POSIX::ctime($then_time) . " was after " . POSIX::ctime($now_time) . "\n"; }

    All that fun and POSIX comes with core perl.

    Update:Oops, thanks rob_au for catching my typo.


    cp
    ----
    "Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic."
      Excellent post. Just one point which I would pick up on, is that values for the month, weekday and day of the year passed to POSIX::mktime begin at zero. As such, the determination of $then_time in your post should alternatively read:

      my $then_time = POSIX::mktime ( 0, # Seconds 0, # Minutes 0, # Hours $date_parts[1], # Day (of month) $date_parts[0] - 1, # Month $date_parts[2] - 1900 # Year );

      This behaviour is documented on the POSIX module man page.

       

      perl -le 'print+unpack"N",pack"B32","00000000000000000000001001100100"'

Re: help on getting date
by data64 (Chaplain) on Jun 03, 2003 at 03:24 UTC

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