Item1547: CalendarPlugin wishlist: ISO 8661 dates as input

I find it handy to be able to have ISO 8661 dates (at least YYYY-MM-DD) in CalendarPlugin.

Patch for Foswiki 2.1.8:

--- Foswiki-2.1.8/lib/Foswiki/Plugins/CalendarPlugin/Core.pm.orig       2024-01-17 21:57:45.552355592 +0100
+++ Foswiki-2.1.8/lib/Foswiki/Plugins/CalendarPlugin/Core.pm    2024-01-17 22:14:24.717738963 +0100
@@ -52,6 +52,8 @@
 my $periodic_rx         = "E([0-9]+)\\s+$full_date_rx";
 my $numdaymon_rx        = "([0-9L])\\s+($wdays_rx)\\s+($months_rx)";

+my $iso_date_rx = "($years_rx)-([0-9][0-9])-([0-9][0-9])";
+
 #TODO: really should replace this naive regex code with a parser that can build up dates using the &dash's as delimiters.
 #or, as a slightly lazyer option, remove the need for an 'ordered' processing by using the &dash..
 #accepted date and interval definitions
@@ -82,6 +84,10 @@
         pattern => $full_date_rx,
         keys    => [qw(name dd mm yy xs xcstr descr )]
     },
+    'ISO-8861 dates' => {
+        pattern => $iso_date_rx,
+        keys    => [qw(name yy mm dd xs xcstr descr )]
+    },
     'anniversary dates' => {
         pattern => "$anniversary_date_rx",
         keys    => [qw(name dd mm yy xs xcstr descr )]
@@ -732,6 +738,17 @@
                   if $@ && (TRACE);
             }

+            if ($d->{name} eq 'ISO-8861 dates') {
+                eval {
+                    if ($d->{yy} == $y && $d->{mm} == $m )
+                    {
+                        _highlightDay($cal, $d->{dd} + 0, $d->{descr}, %options);
+                    }
+                };
+                Foswiki::Func::writeWarning( PLUGINNAME . ": $@ " )
+                  if $@ && (TRACE);
+            }
+
             # collect all anniversary dates
             if ( $d->{name} eq 'anniversary dates' ) {
                 eval {
@@ -1370,6 +1387,7 @@
         'intervals with year',
         'intervals without year',
         'dates with year',
+        'ISO-8861 dates',
         'anniversary dates',
         'dates without year',
         'monthly repeaters',

Much older patch as reference:

--- ./lib/Foswiki/Plugins/CalendarPlugin.pm-2009-04-29  2009-04-29 18:56:18.000000000 +0000
+++ ./lib/Foswiki/Plugins/CalendarPlugin.pm     2009-04-29 18:58:31.000000000 +0000
@@ -556,6 +556,7 @@
        local $weekly_rx = "E\\s+($wdays_rx)";
        local $periodic_rx = "E([0-9]+)\\s+$full_date_rx";
        local $numdaymon_rx = "([0-9L])\\s+($wdays_rx)\\s+($months_rx)";
+        local $iso_8601 = "\\s*(\\d\\d\\d\\d)\\-(\\d\\d)\\-(\\d\\d)\\s*";
 
        # Keep only bullet lines from the text. Note that this is done
        # inside the loop because as each pattern is matched by
@@ -566,6 +567,22 @@
 
        my @bullets = grep { /^\s+\*/ } split( /[\n\r]+/, $text );
 
+        # collect standard dates (ISO-8601)
+        @days = fetchDays($iso_8601, \@bullets);
+        foreach $d (@days) {
+           ($yy, $mm, $dd, $xs, $xcstr, $descr) = split(/\|/, $d);
+            eval {
+                # hack
+                $mm += 0;
+                $dd += 0;
+ 
+                if ($yy == $y && $mm == $m) {
+                    &highlightDay( $cal, $dd, $descr, %options);
+                }
+            };
+            &Foswiki::Func::writeWarning( "$pluginName: $@ " ) if $@ && $debug;
+        }
+  
        # collect all date intervals with year
        @days = fetchDays( "$full_date_rx\\s+-\\s+$full_date_rx", \@bullets );
        $multidaycounter = 0;