Precisely. You simply can't use only UTC locally. You need to develop a system of keeping track of local time. And it can't just be a personal system because yo

Precisely. You simply can't use only UTC locally. You need to develop a system of keeping track of local time. And it can't just be a personal system because you need to figure out equivalents for everyone in the same area (when good times for work schedules or for business hours are). So you need to have an official, standardized system of keeping track of local time information. And in the end you have time zones again.