Adjust test value so that timezone has no effect

If the test is run in a timezone that is behind UTC it fails because
the time generated is ahead of 0000-01-01 00:00:00. Just increase the
time subtracted so that timezone has no effect.

activerecord/test/cases/adapters/postgresql/timestamp_test.rb

@@ -77,7 +77,7 @@ def test_postgres_agrees_with_activerecord_about_precision
   end
 
   def test_bc_timestamp
-    date = Date.new(0) - 1.second
+    date = Date.new(0) - 1.week
     Developer.create!(:name => "aaron", :updated_at => date)
     assert_equal date, Developer.find_by_name("aaron").updated_at
   end