How can I create relative/approximate dates in Perl?

Question

I'd like to know if there are any libraries (preferably DateTime-esque) that can take a normal date time and create an appropriate relative human readable date. Essentially the exact opposite of the more common question: How can I parse relative dates with Perl?.

Obviously, the exact wording/interpretation is up to the actual implementation, but I'm looking to provide a consistent way to specify dates in the future. Knowing an apporximation like "due in 2 weeks" is (to me) more helpful in getting a grasp of how much time I have remaining than something "due on 2009-07-30".

Examples:

2009-07-06        => "in 1 year"
2009-07-30        => "in 2 weeks"
2009-07-09        => "tomorrow"
2009-07-09 12:32  => "tomorrow at 12:32"
2009-07-12 05:43  => "monday morning"
2009-07-03 05:74  => "6 days ago"

Answer 1

Update: It looks like this functionality is implemented in a Template Toolkit Plugin. I am leaving the rest of my answer here for reference, but Template::Plugin::DtFormatter might be the best place to look.

Looking at the source code of that module, I was lead to DateTime::Format::Natural which seems related to what you want.

Previous Answer:

Look into Date::Calc to give you deltas using Delta_DHMS. You should be able to use those deltas to choose how you are going to phrase the date.

Here is a very rudimentary starting point. It is buggy but illustrates the basic idea. Add logic to taste.

#!/usr/bin/perl

use strict;
use warnings;

use Date::Calc qw(:all);
use Lingua::EN::Inflect qw( NO );

my @dates = (
    [ 2009, 7,  6 ],
    [ 2009, 7, 30 ],
    [ 2009, 7,  9 ],
    [ 2009, 7,  9, 12, 32 ],
    [ 2009, 7, 12,  5, 43 ],
    [ 2009, 7,  3,  5, 14 ],
    [ 2010, 8, 9 ],
    [ 2012, 8, 9 ],
    [ 2013, 8, 9 ],
);

for my $date ( @dates ) {
    print "@$date: ", relative_when( $date ), "\n";
}

sub relative_when {
    my ($year, $month, $day, $hour, $min, $sec) = @{ $_[0] };
    my ($Dyear, $Dmon, $Dday, $Dhr, $Dmin, $Dsec) = Delta_YMDHMS(
        Today_and_Now(),
        $year, $month, $day, $hour || 0, $min || 0, $sec || 0
    );
    return NO('year',  $Dyear )     if $Dyear > 0;
    return NO('month', $Dmon )      if $Dmon  > 0;
    return NO('week',  int($Dday/7) if $Dday  > 6;
    return NO('day',   $Dday)       if $Dday  > 1;
    return 'tomorrow' if $Dday == 1;
    return 'today'    if $Dday == 0;
    return "";
}

__END__

Output:

C:\Temp> dfg
2009 7 6:
2009 7 30: 2 weeks
2009 7 9: today
2009 7 9 12 32: today
2009 7 12 5 43: 2 days
2009 7 3 5 14:
2010 8 9: 1 year
2012 8 9: 3 years
2013 8 9: 4 years

Answer 2

Look at the Relative Time Scripts on the Twitter Fan Wiki.

Answer 3

Date::Manip is very powerful for stuff like this, but slower than Date::Calc.