I like a lot this type of investigations. So sometimes is good to be of a timezone far away from the typical triggertime… if the triggertime is in your nighttime, no problem.
When is the trigger time?
For me it’s the same moment, when they send the Passes, or when start any special event (Waterweek, etc). Here in Spain this is at 22 O’Clock Summertime, in case of the passes on sunday.
It was ~19:45 for a long time in the Netherlands. Last wave here came arround 22:00 like @bagguille says… That actually might be the reason we have 7 locations this time. Our last raid dissapears at 21:45.