diff --git a/addons/resource/resource.py b/addons/resource/resource.py
index ca31366ba40..dd96c15bce7 100644
--- a/addons/resource/resource.py
+++ b/addons/resource/resource.py
@@ -20,6 +20,7 @@
 ##############################################################################
 
 import datetime
+from datetime import timedelta
 from dateutil import rrule
 from dateutil.relativedelta import relativedelta
 from operator import itemgetter
@@ -338,8 +339,8 @@ class resource_calendar(osv.osv):
         working_intervals = []
         tz_info = fields.datetime.context_timestamp(cr, uid, work_dt, context=context).tzinfo
         for calendar_working_day in self.get_attendances_for_weekdays(cr, uid, id, [start_dt.weekday()], context):
-            x = work_dt.replace(hour=int(calendar_working_day.hour_from))
-            y = work_dt.replace(hour=int(calendar_working_day.hour_to))
+            x = work_dt.replace(hour=0, minute=0, second=0) + timedelta(seconds=(calendar_working_day.hour_from * 3600))
+            y = work_dt.replace(hour=0, minute=0, second=0) + timedelta(seconds=(calendar_working_day.hour_to * 3600))
             x = x.replace(tzinfo=tz_info).astimezone(pytz.UTC).replace(tzinfo=None)
             y = y.replace(tzinfo=tz_info).astimezone(pytz.UTC).replace(tzinfo=None)
             working_interval = (x, y)