The strategy attached is to do rebalancing every N trading days. The idea is to use self.dayscount to count the days. When self.dayscount % N ==0, update the universe and do rebalancing.  After checking the Log information, I find two issues:

 (1) The first trading in Log is 2017-01-20 but I set the start date as 2017-01-01. 

 (2) The universe update Log messages are missing on 2017-05-22 (day 100) and 2017-11-20 (day 250).