Allow quoted date in front matter defaults

lib/jekyll/frontmatter_defaults.rb

@@ -30,6 +30,13 @@ module Jekyll
       set
     end
 
+    def parse_quoted_date(set)
+      return set unless set.key?('values') && set['values'].key?('date')
+      return set if set['values']['date'].is_a?(Time)
+      set['values']['date'] = Utils.parse_date(set['values']['date'], "Front matter defaults does not have a valid date.")
+      set
+    end
+
     # Finds a default value for a given setting, filtered by path and type
     #
     # path - the path (relative to the source) of the page, post or :draft the default is used in
@@ -159,7 +166,7 @@ module Jekyll
 
       sets.map do |set|
         if valid?(set)
-          update_deprecated_types(set)
+          parse_quoted_date(update_deprecated_types(set))
         else
           Jekyll.logger.warn "Defaults:", "An invalid front-matter default set was found:"
           Jekyll.logger.warn "#{set}"

test/test_front_matter_defaults.rb

@@ -175,4 +175,29 @@ class TestFrontMatterDefaults < JekyllUnitTest
     end
   end
 
+  context "A site with front matter defaults with quoted date" do
+    setup do
+      @site = Site.new(Jekyll.configuration({
+        "source"      => source_dir,
+        "destination" => dest_dir,
+        "defaults" => [{
+          "values" => {
+            "date" => "2015-01-01 00:00:01"
+          }
+        }]
+      }))
+    end
+
+    should "not raise error" do
+      @site.process
+    end
+
+    should "parse date" do
+      @site.process
+      date = Time.parse("2015-01-01 00:00:01")
+      assert @site.pages.find { |page| page.data["date"] == date }
+      assert @site.posts.find { |page| page.data["date"] == date }
+    end
+  end
+
 end