Just to counter, you’d still know this. Forget beats and say there was a single time zone with the normal time system. So right now you know that Eastern time is -5 and people generally do shit 9am to 5pm, and if you live in London you’ll minus 5 from your time yo know the things you mentioned. In a single time zone system, you’ll just know those guys in that region of the US generally do shit from 4am to 1pm. It’s the same thing as remembering a time zone and minussing 5 each time. It is however helpful to coordinate stuff. Like a call at 10am is 10am for everyone (the amount of daylight would differ but you’ll still pick up the phone at 10am). Or a flight that takes off at noon and reaches at 7pm would be exactly the same time everywhere.