Times can now evolve to dates. Closes mongoid#31

lib/origin/extensions/time.rb

@@ -5,6 +5,18 @@ module Extensions
     # This module contains additional time behaviour.
     module Time
 
+      # Evolve the time as a date, UTC midnight.
+      #
+      # @example Evolve the time to a date query format.
+      #   time.__evolve_date__
+      #
+      # @return [ Time ] The date at midnight UTC.
+      #
+      # @since 1.0.0
+      def __evolve_date__
+        ::Time.utc(year, month, day, 0, 0, 0, 0)
+      end
+
       # Evolve the time into a utc time.
       #
       # @example Evolve the time.

spec/origin/extensions/time_spec.rb

@@ -318,6 +318,21 @@
     end
   end
 
+  describe "#__evolve_date__" do
+
+    let(:time) do
+      Time.new(2010, 1, 1, 12, 0, 0)
+    end
+
+    let(:evolved) do
+      time.__evolve_date__
+    end
+
+    it "returns midnight utc" do
+      evolved.should eq(Time.utc(2010, 1, 1, 0, 0, 0))
+    end
+  end
+
   describe "#__evolve_time__" do
 
     let(:time) do