On March 10, 2020, I wrote How Long Will the COVID-19 Epidemic Last? Napkin Calculation. Quoting,

In  the world of this very rough estimate, the epidemic takes a downturn 65 weeks from present. It assumes  no modifications by medicine and public health, and a lot of mostly avoidable human suffering.

It was offered almost tongue in cheek, yet the errors seem to have canceled out. Were it not for the Delta variant, it might be somewhat durable. Since this is a teaching blog, it would be dishonest to claim accuracy. I claim luck instead.

It should be taken as general encouragement of napkin calculations, which have a major advantage over sophisticated modeling:

You can’t be a prisoner of a napkin.