diff --git a/karbor/services/operationengine/engine/triggers/timetrigger/timeformats/calendar_time.py b/karbor/services/operationengine/engine/triggers/timetrigger/timeformats/calendar_time.py
index 54af7d17..8c01f0d7 100644
--- a/karbor/services/operationengine/engine/triggers/timetrigger/timeformats/calendar_time.py
+++ b/karbor/services/operationengine/engine/triggers/timetrigger/timeformats/calendar_time.py
@@ -11,7 +11,7 @@
 #    under the License.
 import os
 
-from datetime import timedelta
+from datetime import datetime
 from dateutil import rrule
 from icalendar import Calendar
 from oslo_serialization import jsonutils
@@ -121,23 +121,9 @@ class ICal(timeformats.TimeFormat):
         :return: int(seconds) or None
 
         """
-        gen = self.rrule_obj
-        kwargs = FREQ_TO_KWARGS[self.min_freq]
-        endtime = self.dtstart + timedelta(**kwargs)
-
-        deltas = []
-        t0 = None
-        for dt in gen:
-            if dt > endtime:
-                break
-            t1 = t0
-            t0 = dt
-            if t1 is None or t0 is None or dt <= self.dtstart:
-                continue
-            delta = timeutils.delta_seconds(t1, t0)
-            if delta:
-                deltas.append(delta)
-        if len(deltas):
-            return min(deltas)
-        else:
+        try:
+            t1 = self.compute_next_time(datetime.now())
+            t2 = self.compute_next_time(t1)
+            return timeutils.delta_seconds(t1, t2)
+        except Exception:
             return None
diff --git a/karbor/tests/unit/operationengine/engine/triggers/timetrigger/timeformats/test_calendar_time.py b/karbor/tests/unit/operationengine/engine/triggers/timetrigger/timeformats/test_calendar_time.py
index 0223f293..8a51f144 100644
--- a/karbor/tests/unit/operationengine/engine/triggers/timetrigger/timeformats/test_calendar_time.py
+++ b/karbor/tests/unit/operationengine/engine/triggers/timetrigger/timeformats/test_calendar_time.py
@@ -173,3 +173,13 @@ class CalendarTimeTestCase(base.TestCase):
         dtstart = datetime(2016, 2, 20, 17, 0, 0)
         time_obj = calendar_time.ICal(dtstart, pattern)
         self.assertIsNone(time_obj.get_min_interval())
+
+    def test_get_min_interval_when_interval_is_bigger_than_default_rate(self):
+        pattern = (
+            "BEGIN:VEVENT\n"
+            "RRULE:FREQ=MINUTELY;INTERVAL=5;\n"
+            "END:VEVENT"
+        )
+        dtstart = datetime(2016, 2, 20, 17, 0, 0)
+        time_obj = calendar_time.ICal(dtstart, pattern)
+        self.assertEqual(300, time_obj.get_min_interval())