It's the thing that baffles me the most with those people, the Knuths and Lamports and Carmarcks, and whatnot.

It's not like they have light schedules - they do research, they have classes, they attendconference, and they have jobs, etc...

And some benefit from tenure, which give them time to deeply focus on some topics.

But I can't imagine how I would write tex in ten years in Pascal on archaic machines if I had all the time to myself.

Doing that in the middle of understanding more computer science than my eyes would ever read ?

What do they do with their time ? What do they don't do ? Are they able to skip the eating and pooping and sleeping and cleaning their house and picking up parcels at the post office and grocery shopping parts ?

Or a proto Unix being written in three weeks. Concretely, what are the days of those three weeks made of ? Especially since it's famously when the spouse was NOT there to handle the housekeeping...

I see not amount of "life hacks" and "atomic habits" and whatnot helping with that. But it's probably just as natural to them as biking - and you can't explain biking, I guess ?