Martian Clock using Standard Seconds

written by Dale Shultz, November 11, 1999

A Martian clock must balance two competing considerations:

  1. It should be based on the standard second, so that our accumulated scientific knowledge can be used without constant conversions.
  2. It should use days that are divisible by an even number of units, and that do not involve fractional hours, or hours with a varying number of minutes.

Unfortunately, Martian solar days are 24 hours, 39 minutes and 35.247 seconds long, so most observers have concluded that a day based on standard seconds would have to include fractional hours, or a constant barrage of leap seconds.

I am proposing a clock, which is based on standard seconds, does not use fractional hours, and does not require any more manual effort than we currently use for daylight savings time. It will continue to use familiar minutes that are 60 seconds long. Note that a Martian day is almost exactly 1480 minutes long; so it can be divided into 20 hours of 74 minutes each. In fact, the Martian day is 1479 minutes and 35.247 seconds long, so at the end of the day the clock will be 24.753 seconds ahead of mean solar time.

After 180 days, the time difference will be 4455.54 seconds. That is almost the same as the length of a Martian hour (74 minutes * 60 sec/min = 4440 seconds). So we can get back to mean solar time by setting the clock back one hour every 180 days.

Note that on Earth, we set our clocks every 182.5 days, and that the change is either backward or forward, while on Mars, the clocks are always set back. (Martians always get an extra hour of sleep.) Finally, note that every 77 Martian years we will need an additional leap hour to mop up the residual time difference.

(An alternate scenario is to use days that have 37 hours of 40 minutes each. In that case, we would set the clock back by one hour every 97 days.)

Copyright 1999 by Dale Shultz, all rights reserved.