add offset for fog times

allows working around clock skew issues

lib/fog/aws/requests/storage/sync_clock.rb

@@ -0,0 +1,28 @@
+module Fog
+  module AWS
+    class Storage
+      class Real
+
+        # Sync clock against S3 to avoid skew errors
+        #
+        def sync_clock
+          response = begin
+            get_service
+          rescue => error
+            error.response
+          end
+          Fog::Time.now = Time.parse(response.headers['Date'])
+        end
+
+      end # Real
+
+      class Mock # :nodoc:all
+
+        def sync_clock
+          true
+        end
+
+      end # Mock
+    end # Storage
+  end # AWS
+end # Fog

lib/fog/aws/storage.rb

@@ -42,6 +42,7 @@ module Fog
       request :put_object_acl
       request :put_object_url
       request :put_request_payment
+      request :sync_clock
       request :upload_part
 
       module Utils

lib/fog/core.rb

@@ -29,4 +29,5 @@ require 'fog/core/provider'
 require 'fog/core/service'
 require 'fog/core/ssh'
 require 'fog/core/storage'
+require 'fog/core/time'
 require 'fog/core/wait_for'

lib/fog/core/time.rb

@@ -0,0 +1,21 @@
+module Fog
+  class Time < ::Time
+    class << self
+
+      def now
+        ::Time.now - offset
+      end
+
+      def now=(new_now)
+        old_now = ::Time.now
+        @offset = old_now - new_now
+        new_now
+      end
+
+      def offset
+        @offset ||= 0
+      end
+
+    end
+  end
+end