He thinks we should all use GMT instead:
[W]ithin a given time zone, the point of a common time is not to force everyone to do everything at the same time. It's to allow us to communicate unambiguously with each other about when we are doing things.
If the whole world used a single GMT-based time, schedules would still vary. In general most people would sleep when it's dark out and work when it's light out. So at 23:00, most of London would be at home or in bed and most of Los Angeles would be at the office. But of course London's bartenders would probably be at work while some shift workers in LA would be grabbing a nap. The difference from today is that if you were putting together a London-LA conference call at 21:00 there'd be only one possible interpretation of the proposal. A flight that leaves New York at 14:00 and lands in Paris at 20:00 is a six-hour flight, with no need to keep track of time zones. If your appointment is in El Paso at 11:30 you don't need to remember that it's in a different time zone than the rest of Texas.
It's even easier to get people to use International System measurements than to get them to understand the arbitrariness of the clock, but let's unpack just one thing Yglesias seems to have missed: the date.
Imagine you actually can get people in Los Angeles to use UTC. Working hours are 16:00 to 24:00. School starts at 15:45 (instead of ending then). In the summer, the sun rises at 12:30 and sets at 02:00.
Wait, what? The sun sets at 2am? So...you come home on a different day? That makes no sense to most people.
Yes, in a world where people are unwilling to give up their 128-ounce gallons and 36-inch yards in favor of 1000-milliliter liters and 100-centimeter meters, a world where ice freezing at 32 and boiling at 212 makes more sense than freezing at 0 and boiling at 100, a world where Paul Ryan is thought to be a serious person, we're not moving away from the day changing while most people are asleep.
And don't even get me started on the difference between GMT and UTC.