The scheduling of Shinken Enterprise is quite simple. The first scheduling take care of the max_service_check_spread and max_host_check_spread so the time of the first schedule will be in the

start+max_*_check_spread

if the Check Period agree with it. Shinken Enterprise use a random way of doing it : the check is between t=now and t=min(t from next timeperiod, max_*_check_spread), but in a random way. So you will will have the better distribution of checks in this period.

After this first scheduling, the time for the next check is just t_check+check_interval if the timepriod is agree for it (or just the next time available in the timeperiod).