fix #856 where DateTimes supplied through the rest api was not converted to the users timezone

app/models/preference.rb

@@ -25,7 +25,7 @@ class Preference < ActiveRecord::Base
     date = nil
 
     if s.is_a?(Time)
-      date = s.to_date
+      date = s.in_time_zone(time_zone).to_date
     elsif s.is_a?(String)
       date = Date.strptime(s, date_format)
     else