Probe outages of a peculiar length.

I have two access points that have about 90% of their outages that are either 3:00 or 3:30 . Not about those times but exactly those times. To me that looks like something different than a normal outage. But I cannot find anything in the settings that are set for that sort of time, and nothing is logged. I was wondering if those times mean anything specific. Any help would be appreciated.