Different employers in areas have their own arbitrary start/stop times already, time numbers are already an arbitrary concept, if someone in CA right now is working hours based on NY, when they work relative to the sun won’t change, just the numbers. The difference would be in people cold contacting others vs scheduled times. Right now if something is scheduled you have to convert it to your time, the formula for which will vary based on what time zone it is scheduled in. With this change, when reaching out to someone far away, you’d have to figure out if you’re contacting them at an appropriate time for their day/night, but that’s also inexact because people have different personal cycles anyway.

Working hours being 9am-5pm vs 1900-0300 are just numbers.