With the lack of precision for clocks the way they are, and worries about variance in travel time due to traffic, distractions, potty emergencies, and so forth,

With the lack of precision for clocks the way they are, and worries about variance in travel time due to traffic, distractions, potty emergencies, and so forth, the more natural way to handle precision is to give yourself a 5-to-15-minute-to-an-hour buffer to ensure that you're in your seat when the clock ticks from 11:59 to 12:00. And yes, 5-to-15-to-an-hour is something that varies, depending on the length of your trip. 5 is appropriate when you're in your office and you need to get to the conference room, 15 if you're driving from your nearby home, an hour if you're flying in, or if you have to drive 200 miles or so -- particularly if it's a trip you don't regularly take! For meetings, I actually give myself 16 "precise" minutes -- one minute less than 15, with 4-minute-30-second snoozes, so I can have both adequate warning, and regular pokes, to make sure I can do something on time.