Anyone notice sales increase at certain times of month?

I have spikes in the middle of every month for sales. I don’t do much around that time to incite new sales. Wondering if it has to do with paychecks arriving at that time? New money in pocket? Would think I would see a spike at end of month, but it’s small in comparison. Guessing rent is due T end of month and that is why buying is t as strong as middle of month?