What's your longest day ever on set?

Okay, I'm not talking about portal-to-portal: what's the longest you've spent, on the clock, working on a set in one day?

I had some friends on the SNL film unit talk about a hellscape of 18 hours, but I know they mostly do two separate crews with separate shifts if they can staff it.

My personal record is 16.75 hours, sadly on a union majors movie. That was a lucrative but horrible day.