January 13, 2020:

Cashier: Skinny Cows again today.

Mark: I'm on an all Skinny Cow diet. It's a science experiment.

Cashier (looking partly credulous, as though there might be sincerity in that absurdity): How's it working out for you?

Mark: Good, I think. Well — I'm 170 years old, so, it seems to be doing something...

Cashier, looks at Mark with utter bafflement, trying to decide if he's having her on, or not.

Mark, leaves the store feeling considerably older than when he arrived.