This document is part of the Martian Time Boneyard. It was originally located at
Author: Ben Weiss

A Timekeeping System For Mars

On Mars, the solar "day" is 24 hours, 39 minutes and 35 seconds long.

This presents obvious difficulties in the design of a simple Martian timekeeping system, especially one based on our familiar units of time (i.e., hours, minutes, seconds). Unless a new unit of time (to replace the metric second) is introduced, the Martian day will not be cleanly divisible into existing units. Both of these possibilities are distasteful from a simplicity standpoint, but at first it seems impossible to avoid one or the other.

Therefore, I would like to propose an elegant solution to this problem, which diverges from other proposed solutions in one simple aspect: it varies the length of the day!

This is actually not such a far-fetched concept. Think of Earth's calendar: The year alternates between 365 and 366 days (leap-years), months vary from 28 to 31 days, and even the occasional day lasts 23 or 25 hours (daylight savings time). Even a leap-second is sometimes added, to keep things on track.

Also, there's nothing magical about each day having to be exactly the same length. Sunrise and sunset don't happen at the exact same time each day, but vary with the season. How important is it, really, that the time interval between 7am one morning and 7am the next morning be exactly 24 hours? Not too critical. We all go through the hassle of daylight savings time, twice a year, and survive just fine... Actually, the biggest problem seems to be remembering to set the clock back!

So, in a nutshell, here is my proposal for Martian time:

Mars should operate on a 6-day "week," with four 25-hour weekdays, followed by two 24-hour weekends.

The "average" day in this calendar works out to 24 hours and 40 minutes, which matches the actual Martian day to within 25 seconds, or an overall error of only 0.028%. This slight inaccuracy can be corrected by having "three-day weekends" at the equinoxes and solstices, effectively subtracting a "leap hour" each time this happens. (An additional three-day weekend will be needed in most years, to keep the system on track.)

Of course, there are several other basic issues that any Martian timekeeping system must address:

•Time Zones  -  This system works well with 24 time zones, analogous to those on Earth. The "Date-Line" creates an alternating one-hour or two-hour separation between the adjacent zones, on weekends and weekdays, respectively. All other time-zone boundaries have a constant one-hour separation, just as they do on Earth. The passage of time occurs continuously within each zone; with no "jumping-forward" or "jumping-back" as there is with daylight-savings time on Earth.

•Wristwatches ? Analog wristwatches could show a 24-hour clock, where the hour hand pauses at weekday midnight while the minute hand completes one extra revolution (to represent the 25th hour of the day).  (Does anyone know whether this is mechanically feasible?)

•Astronomy - Conversion between this Martian calendar and "sidereal" time would be no more difficult than from the Earth calendar. Thus, astronomical observations, which are one of very few tasks that depend on a "clockwork" constant day, would not suffer from this timekeeping system.

And of course, there would be several benefits of this system:

•Compatibility - This system is compatible with (and independent of) any proposed subdivision of the Martian year into months, which is (if anything) an even more contentious point than the smaller-scale timekeeping addressed here.

•Parity - The "hour" interval can be synchronized with Earth, so that, e.g. midnight on Earth will correspond to exactly (say) 6pm in a particular zone on Mars, but not, say, 6:43:27pm. Switching time-zones between Mars and Earth would thus involve adjusting the hour, but not fiddling with minutes or seconds (or worse yet, converting to and from a Mars-based unit of time)! This is one of the most valuable features of this timekeeping system, in my opinion.

•Psychology - The continued use of familiar time units (seconds, minutes, hours, days, weeks) would do wonders for the sanity of anyone involved with Mars exploration or colonization. The 6-day week is close enough to the familiar 7-day week to "feel" about the same, providing a natural multi-day cycle of work and rest. (Rationale: the weekdays are longer, so it's only natural that there's one fewer of them than on Earth, and the weekends provide time to recuperate from the "jet-lag" induced by the longer weekdays.)  And, tongue-only-partially-in-cheek, I propose the following naming convention:

Sunday, Tuesday, Wednesday, Thursday, Friday, Saturday.  ;)

Tell me what you think!