The number on the clock is by convention, I used to go to work at 2am, I worked nights.
If everyone just published hours in UTC, and availability in UTC, this would work fine. You'd know that normal working hours for your area are you know, 1200-2000 UTC.
Makes sense, that would also work. However, there is another case where the question comes: what is the best time for a meeting between San Francisco, New York, London, and Berlin for example? Here it becomes a bit challenging as we lost the meaning of local hours for those locations. 2am in most cases means sleeping time, not for everyone, but mostly. With only UTC we'd lose the semantics meaning of local hours. Hence combining local hours and UTC in one clock face.
The number on the clock is by convention, I used to go to work at 2am, I worked nights.
If everyone just published hours in UTC, and availability in UTC, this would work fine. You'd know that normal working hours for your area are you know, 1200-2000 UTC.