Nine people messaged me between the time I left and the time I returned in the morning. The first two were pretty early on around 7pm. Then there was a gap until people messaged me at 11:50, 12:47, 2:36, 2:54 (and the same person again at 5:13), 3:28, and 3:37. Then one more at about 9am as I was returning to the office.
I guess a significant portion of my contact list are night owls.