Fixed Datetime validation

Author: Richard Degenne

lib/rdf/model/literal/datetime.rb

@@ -6,7 +6,7 @@ module RDF; class Literal
   # @since 0.2.1
   class DateTime < Literal
     DATATYPE = RDF::URI("http://www.w3.org/2001/XMLSchema#dateTime")
-    GRAMMAR  = %r(\A(-?\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?)((?:[\+\-]\d{2}:\d{2})|UTC|GMT|Z)?\Z).freeze
+    GRAMMAR  = %r(\A(-?(?:\d{4}|[1-9]\d{4,})-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?)((?:[\+\-]\d{2}:\d{2})|UTC|GMT|Z)?\Z).freeze
     FORMAT   = '%Y-%m-%dT%H:%M:%S%:z'.freeze
 
     ##

spec/model_literal_spec.rb

@@ -694,6 +694,10 @@ def self.literals(*selector)
         2010-01-01T01:00:00+01:00
         2009-12-31T23:00:00-01:00
         -2010-01-01T00:00:00Z
+        20010-01-01T00:00:00Z
+        -20010-01-01T00:00:00Z
+        0052-01-01T00:00:00Z
+        -0052-01-01T00:00:00Z
       ),
       %w(
         foo
@@ -705,6 +709,10 @@ def self.literals(*selector)
         0000-01-01T00:00:00
         2010-07
         2010
+        52-01-01T00:00:00Z
+        052-01-01T00:00:00Z
+        -52-01-01T00:00:00Z
+        -052-01-01T00:00:00Z
       ) + ['2010-01-01T00:00:00Z foo', 'foo 2010-01-01T00:00:00Z']
 
     context "object values" do