See StatCounter The pattern of two to three one-day spikes on weekdays using GNU/Linux for browsing StatCounter’s universe continues. I’ve noticed that the spikers use Chrome 41 and did not change to Chrome 42 as most users did in this period of time. Chrome 41 had uptake starting around the beginning of March but the spikes in its usage did not start until April 9. That gives another clue. What systems upgrade applications automatically and which do not?
This suggests the spiking systems are a single organization on a single schedule with a single system administrator… Sounds like schools to me but it could also be a large business or government or particular device sold in huge quantity without automatic updating. The 3 spikes on weekdays suggests to me it’s the schools.