add/subtract days/weeks/months/years to/from a date

lib/DDG/Goodie/DateMath.pm

@@ -0,0 +1,84 @@
+package DDG::Goodie::DateMath;
+# ABSTRACT add/subtract days/weeks/months/years to/from a date
+
+use DDG::Goodie;
+use Date::Calc qw( Add_Delta_Days Add_Delta_YM This_Year );
+
+triggers any => qw( plus minus + - );
+zci is_cached => 1;
+zci answer_type => 'date_math';
+
+handle query_lc => sub {
+    my @param = split /\s+/;
+    return unless scalar @param == 4;
+
+    my ( $date, $action, $number, $unit ) = @param;
+
+    # check/tweak input
+
+    # default to this year:
+    my $md_re = '[01]?[0-9]/[0-3]?[0-9]';
+    $date .= '/' . This_Year() if $date =~ /^$md_re$/;
+    return unless $date =~ /^$md_re\/[0-9]{4}$/;
+
+    my %action_map = (
+        plus  => '+',
+        '+'   => '+',
+        minus => '-',
+        '-'   => '-',
+    );
+    $action = $action_map{$action} || return;
+
+    return unless $number =~ /^\d+$/;
+    $number = 0 - $number if $action eq '-';
+
+    $unit =~ s/s$//g;
+
+    # calculate answer
+    my $sub_map = {
+        # sub parameters: year, month, day, number
+        day => sub {
+            return Add_Delta_Days( @_ );
+        },
+        week => sub {
+            $_[3] *= 7; # weeks to days
+            return Add_Delta_Days( @_ );
+        },
+        month => sub {
+            $_[4] = $_[3]; # months
+            $_[3] = 0;     # 0 years
+            return Add_Delta_YM( @_ );
+        },
+        year => sub {
+            push @_, 0; # 0 months
+            return Add_Delta_YM( @_ );
+        },
+    };
+
+    my $sub = $sub_map->{$unit} || return;
+    my $answer;
+    eval {
+        $answer = format_ymd( $sub->( mdy_to_ymd_array( $date ), $number ) );
+    };
+    return if $@;
+
+    # output, using original @param
+    $param[0] = $date; # include the optional year
+    $param[3] = $unit;
+    $param[3] .= 's' if $param[2] > 1; # plural?
+    return "@param is $answer";
+};
+
+sub mdy_to_ymd_array
+{
+    my @date = split '/', shift;
+    return ( $date[2], $date[0], $date[1] );
+}
+
+sub format_ymd
+{
+    # ymd array to m/d/y
+    return join '/', $_[1], $_[2], $_[0];
+}
+
+1;

t/DateMath.t

@@ -0,0 +1,27 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use Test::More;
+use DDG::Test::Goodie;
+
+zci answer_type => 'date_math';
+zci is_cached => 1;
+
+ddg_goodie_test(
+	[qw(
+		DDG::Goodie::DateMath
+	)],
+	'1/1/2012 plus 32 days'  => test_zci( '1/1/2012 plus 32 days is 2/2/2012' ),
+	'1/1 plus 32 days'       => test_zci( '1/1/2012 plus 32 days is 2/2/2012' ),
+	'1/1/2012 plus 5 weeks'  => test_zci( '1/1/2012 plus 5 weeks is 2/5/2012' ),
+	'1/1/2012 plus 5 months' => test_zci( '1/1/2012 plus 5 months is 6/1/2012' ),
+	'1/1/2012 PLUS 5 years'  => test_zci( '1/1/2012 plus 5 years is 1/1/2017' ),
+	'1/1/2012 plus 1 day'    => test_zci( '1/1/2012 plus 1 day is 1/2/2012' ),
+	'1/1/2012 plus 1 days'   => test_zci( '1/1/2012 plus 1 day is 1/2/2012' ),
+	'1/1/2012 + 1 day'       => test_zci( '1/1/2012 + 1 day is 1/2/2012' ),
+	'1/1/2012 minus 10 days' => test_zci( '1/1/2012 minus 10 days is 12/22/2011' ),
+);
+
+done_testing;
+