Obviously, it would be possible to learn these things, but it's much harder to look up. Imagine a table of different countries, how do you define this stuff? Much easier to define what time the 24 hour day starts based on the sun than to define people's behaviour, as not everyone will have the exact same schedule for when they start work, when they wake up, etc.
For scheduling meetings with people globally, you'd have to figure out the day/night cycle but I doubt it would be all that much different than it is now.
But! There would be no goofy daylight savings time differences and there would be no ambiguity ("Oops, I thought the meeting was at 1pm my time, not yours...").
Plus, all us programmers could sleep peacefully at night knowing that our time-based code would just work, instead of waking in a cold sweat wondering what will happen when a government across the globe decides to erase the existence of a day.
Examples: (for some definitions of here and there) It's 1300 here which means that it's 1700 there - do people tend to go home at 1700 or 1800?
Lunchtime in France is typically 1200-1400 (local), whereas in Israel it is 1400-1600. If I'm in France, and I need to call up my Israeli colleagues after lunch, simply adjusting for timezone won't do. If I call at 1430 Israeli time, they will have just gone out.
In these situations you currently have to know two things: what time it is over there, and what the cultural norms for work and mealtimes are. If time were internationally uniform, you'd only need the latter.
For some time now I've included my time zone in the mouseprint of my email signature block; it'd be easy enough to include one's usual hours of availability as well.
With flexi-time and "24 hour working", that's becoming difficult with even the current system. I don't know the hours most of my contacts work but it frequently seems to be well into the small hours..
EDIT: s/things/thinks/
There is no net benefit.
I propose that we just drop DST, base local time on solar noon and calculate our associates' time based on their longitude.