Day, once a month. While I'm in a rich nation, over half the population comes from poor countries. On pay day, the grocery store swells to three times normal footfall. There are A LOT of people living near the edge, whose consumption is truly paycheck to paycheck.

In fairness, most of these guys are selflessly sending most of their paychecks back home, but logic still would hold that they'd plan their remaining spending to spread out across a month, but they don't.

Human behavior is a funny thing. As a marketer, I view my whole job as exploiting human irrationality. I sleep at night knowing my target audience can afford frivolity, not these guys.