Loosen @Date handling, do not require specific format

CHANGES.md

@@ -28,6 +28,10 @@ This file describes changes in the AutoDoc package.
     `@Command` does not start at column 1
   - Normalize parsed `InstallMethod` names by stripping surrounding
     quotes, matching `Declare...` handling
+  - Loosen requirements on `@Date` command: this used to allow free form,
+    but in recent versions was restricted to dates of the form YYYY-MM-DD
+    or DD/MM/YYYY; now we again allow any text, but text in those specific
+    formats is still parsed and formatted (e.g. 2026-03-08 as 8 March 2026)
   - Improve parser robustness by reporting clear EOF errors for
     unterminated declaration headers and filter lists
   - Make tests work when the package directory is read-only by writing

gap/AutoDocMainFunction.gi

@@ -223,7 +223,8 @@ end );
 ## separately.
 InstallGlobalFunction( CreateTitlePage,
   function( dir, argument_rec )
-    local indent, tag, names, filestream, entity_list, OutWithTag, Out, i;
+    local indent, tag, names, filestream, entity_list, OutWithTag, Out, i,
+          parsed_date;
 
     filestream := AUTODOC_OutputTextFile( dir, "title.xml" );
     indent := 0;
@@ -271,11 +272,17 @@ InstallGlobalFunction( CreateTitlePage,
     fi;
 
     if IsBound( argument_rec.Date ) then
-        # try to parse the date in format DD/MM/YYYY (we also accept single
-        # digit day or month, which is formally not allowed in PackageInfo.g,
-        # but happens in a few legacy packages)
-        argument_rec.Date := Chomp( argument_rec.Date ); # remove trailing newlines, if present
-        OutWithTag( "Date", AUTODOC_FormatDate(argument_rec.Date) );
+        if IsString( argument_rec.Date ) then
+            argument_rec.Date := Chomp( argument_rec.Date ); # remove trailing newlines, if present
+
+            # PackageInfo.g dates are normalized, but @Date should also allow
+            # free-form text when the input is not one of the supported date formats.
+            parsed_date := AUTODOC_ParseDate( argument_rec.Date );
+            if parsed_date <> fail then
+                argument_rec.Date := AUTODOC_FormatDate( parsed_date );
+            fi;
+        fi;
+        OutWithTag( "Date", argument_rec.Date );
     fi;
 
     for i in [ "Address", "Abstract", "Copyright", "Acknowledgements", "Colophon" ] do

tst/worksheets/autoplain.expected/title.xml

@@ -6,6 +6,6 @@
     Plain file.autodoc Test
   </Title>
   <Date>
-    30 August 2018
+    8 March 2026
   </Date>
   </TitlePage>

tst/worksheets/autoplain.sheet/plain.autodoc

@@ -1,5 +1,5 @@
 @Title Plain file.autodoc Test
-@Date 2018-08-30
+@Date 8 March 2026
 
 # Test
 Does AutoDoc have a way to allow that header block not to appear in