Correction: the nth day was off by 1 when it was exactly a multiple of 7.

For exemple monday the 28th was marked as the fifth monday of the month, wrong!!!

lib/schedule.rb

@@ -11,7 +11,7 @@ module Schedule
   def prepare_schedule
     r = IceCube::Rule.send rule.split('_').first
     if rule == 'monthly_day'
-      r.day_of_week start_time.wday => [start_time.day / 7 + 1]
+      r.day_of_week start_time.wday => [(start_time.day - 1) / 7 + 1]
     else
       r
     end