Well, when someone asks me what time it is now, I don't say, "The minute hand of my watch is pointing at the 1, and the hour hand slightly past the 3." Instead

Well, when someone asks me what time it is now, I don't say, "The minute hand of my watch is pointing at the 1, and the hour hand slightly past the 3." Instead I translate it to "three-oh-five". Wouldn't be too much of a stretch to say 15:05 instead. (My point being that many watches and clocks already don't give us the literal time as it's spoken, just a representation.) Edit: although just to be clear, I don't actually think we should switch to a single time zone. It would cause all kinds of headaches. I just think if in some universe it were to happen, it would necessarily go along with a switch to 24h time.