Our Ugly Past

We used to use (and still use, in a few primitive cultures) units like miles, yards, feet, and inches to measure length. These units have a ratio of 63360:36:12:1. Converting among them, while not a complicated process, requires a nontrivial operation. Now that we know better, we use the meter for most measurements of length, along with a standard prefix to scale it to our needs. It's much easier to multiply by 10 or 1000 than 36 or 5280.

Our Ugly Present

Have you ever had to answer a question like this one?

Ned began tying his shoes at 5:23 a.m. He took a 20 minute break for lunch and finished at 3:11 p.m. He spent 25% of his shoe-tying time trying to think of the name of those things at the end of his laces. How much time did Ned spend actually tying his shoes?

I admit it's a stupid example, but the problem is much harder than it needs to be. Why is this problem such a pain? Because the units used to measure time are awkward.

There's no need for this. The angelic souls who gave us the metric system stopped short for some reason. Even in our more civilised nations, people still measure time with years, months, days, hours, minutes, and seconds. This is ridiculous. Since years, months, and days are all based on significant physical phenomena, I'll not pick at those. However, hours, minutes, and seconds (which are 1/24, 1/1440, and 1/86400 of a day, respectively) have no place in any clean system of measurements.

A Snag

Alas, the folks who came up with all this stopped short in another area as well. The list of prefixes is incomplete. Without easy ways of saying 10^-4 and 10^-5, it becomes awkward to talk about the amounts of time we usually talk about in terms of days. We'd have to use microdays and use large numbers (e.g. 1 minute == 694 microdays) or use milidays and use very small numbers (e.g. 1 minute == 0.694 milidays).

My Solution

1 day == 1000 chrons

To give people an idea of how the chron relates to old units, here are some conversions:

 1000 chrons       =   1 day
  250 chrons       =   6 hours
   42 chrons      ~=   1 hour
   10 chrons      ~=  15   minutes
    1 chron       ~=   1.5 minutes (86 seconds)
    1 decichron   ~=   9   seconds
    1 centichron  ~=   0.9 seconds

If timezones are not used (which is an issue I haven't adressed here), then the current time in chrons is almost a simple function of the Modified Julian Date:

  chrons ~ non_integral_portion(MJD) * 1000

I say "almost" because MJD is related to UT, not UTC. If the length of a chron is fixed and the number of chrons is also fixed, MJD and chrons will usually be slightly off.

I can't fix my watch, but I do have various clocks and helpful software for my computer.