This proposal describes three concepts:
1.   a combined timekeeping and mapping system for Mars
2.   a Martian clock, tailored for the special conditions on the Red Planet
3.   a method of utilizing two calendars concurrently.

INTRODUCTION
Thousands of different data about Planet Mars are recorded every day with reference to Earth calendars. It works, but would it not be better to record them on a Martian calendar and timekeeping system? Shouldn’t our engineers and scientists work with clocks that are tailored for the special situation on Planet Mars? They could see Earth and Martian time any moment on their Martian clocks. Watch manufacturers have advanced timekeeping technology so far that we could switch instantaneously from Earth time to Martian time. Should we wait to use a Martian calendar until the first settlers land on Mars?

TIMEKEEPING AND MAPPING SYSTEM
Martian research projects will become more important with every year. And with this increased involvement of scientists, engineers and astronauts the development of a Martian timekeeping system should be done as early as possible. The actual research and the future venture of settling humans on Mars will be an international task comprised of people from many nations and cultures. It is therefore necessary to produce a Martian timekeeping system that can be accepted by all participants. And it must be simple and easy to learn. Several proposals have been made to create timekeeping systems as close to Earth’s clock and calendar systems as possible (Ref.1). The areogator is a practical system to calculate Martian time (Ref.2). And data coming from Mars are recorded every day with exact date and time. But we could use a simple Martian clock for this purpose accepted by people in the United States, in Europe, Japan and Russia. My proposal leaves the units for Earth unchanged. Years, seasons, months, weeks, days, hours, minutes and seconds will continue to be used. Clocks will click continuously and slowly be replaced by digital clocks. However, the units for the Martian clocks are new and should be used exclusively for Martian timekeeping.
I conceived this proposal because my wife is writing a book for teenagers and asked me how Martian settlers would measure time in the year 2050. I believe that the specific conditions on planet Mars require a different system than the Earth’s conventional one. The need to characterize how Martian settlers measure time and describe exact locations of Martian landscape features induced me to develop a system tailored to the specific Martian conditions, one that is universal and uncomplicated in design, using numbers as much as possible. It could assist our scientists and space engineers in their research projects as soon as it is accepted by the scientific community. And later it would be the timekeeping system of the first settlers on Mars.
 

MARTIAN YEARS
Martian settlers measure the time to complete one orbit around the sun and call it one ORB. Martian years are counted in orbs. Each orb has 668 SOLS. Since exactly 668.5990 sols make an orb, 669 sols can be computed in advance and included in the programmed sols of leap years.
 

SOLS
Every SOL  (as we already call Martian days) is determined only by its number. There is no simpler and more direct method. All events planned in the future or in the past can be identified by orbs and sol numbers. Calendars show lists of sol numbers with free space to take notes for appointments and special events. Well-organized Martian settlers have time boards to plan their activities ahead. Birthdays can be celebrated by children who remember their birth-sol number. For example Tom was born in orb 12 on sol 277, his sister in orb 13 on sol 512.

CENTISOLS
Martians would not count 24 hours for each rotation about its axis, but subdivide each sol into 100 CENTISOLS. A specific time of the day would be described simply by calling centisols, beginning at noon when the sun is at its zenith. These numbers would be shown on the Martian settlers’ digital clock. A 3 ½-orb old child (6 Earth years) who has learned to count to 100 would know the time of the sol and understand what the numbers mean. Small numbers from 0 up to 5 would signify lunch time, 25 dinner time, 50 dark night and 75 time to awake. At 77 centisols school would begin and last till 95.50. Decimals would permit as much precision in time measurement as required. Millisols and even microsols could be included in the time description. This simple timekeeping system would eliminate any confusion between Martian and Earth time.
What does a CENTISOL  mean to us? 25 centisols equal 6 Earth hours. 4 centisols are about one Earth hour, one centisol corresponds to roughly 15 Earth minutes.

MAPS OF MARS
This simple timekeeping system becomes practical and advantageous when Martians describe the location of certain features on the Mars surface with a new and simple method which correlates to the timekeeping system.
Martians would not use 360 degrees of longitude. Instead they use 100 MERIDIANS, called MERS, to describe longitude. And since one full rotation of Mars takes place when 100 meridians face the sun over 100 centisols, there is a direct relationship between location and time description. If a Martian feature is located at mer 15, Martians know it is 15 meridians west of the Zero meridian, and the sun will be there at its zenith at the time of 15 centisols. Time and location have identical numbers.
Similar to the meridians of  longitude, the latitude around the Mars surface is divided into 100 equal parts once around the poles, called LATS, + 25 parts to the north pole and - 25 parts to the south pole, counted from the equator. As an example the location of a feature can be described simply as:  76.35 + 25.12.  If more precision is needed it can become an expression such as:  76.352778 + 25.129456.  This would replace the use of the actual Martian mapping system, using 360 degrees for longitude and + and - 90 degrees for latitude. Martians call meridians MERS and the degrees of latitude the LATS. The center of Olympus Mons would lie at about 36.940 + 4.454.
The Martian longitudes begin at 0º in the crater Airy-O in Sinus Meridiani and increase progressively to the west; thus Solis Lacus lies at about 25 mers longitude. Mare Sirenum is at 50 mers; and Indies, the bright area just east of Syrtis Major is at 75 mers. The direction of rotation is the same as that of increasing longitude, that is toward the west at a rate of 1 meridian per 1 centisol. This simple relationship between space and time is one of the most important advantages of this combined time- and station-keeping system.

TIME
Of course the first settlers will not stay at the Zero meridian from which the so called Zero Mars Time counts. Let’s assume they have established their stations close to the meridians 18 and 77. They will then have their local time which they call the “20-Time Zone” and the “80-Time Zone” comparable to Greenwich Mean Time and our local time zones on Earth. The clock can easily be set for these local times by changing only the first digit of the mers, and the daily chores can be done on Mars as they were accustomed to on Earth.
Zero Mars Time would  be used for communication between Mars and Earth.        When traveling longer distances over Mars, Martians would use the Zero Mars Time, too, but after landing they would switch over to the local zone time.
Research projects landing an object on Mars in the future could be made less complicated for scientists by accepting this simple combined timekeeping and mapping system. Existing coordinates would be changed on maps from 360 to 100 and a special Mars clock could be introduced as described later. The advantage attained is the identity of numbers in the description of time and locality: an object has landed at meridian 18.30, a location where the sun will be at its zenith at 18.30 centisols of Zero Mars Time. When switching to the “20-Zone Time” and an applet, the local light situation would become very clear to a scientist far away on Earth.
Since one Mars orbit stretches over exactly 668.5990 sols, the additional time of 0.5990 sols must be added for each sol by a factor of  0.00089 centisol per sol.

OTHER UNITS
Distances would be measured using the metric system as well as surfaces, spaces, elevations and weights. The metric system would be used in general. Temperatures measured in Kelvin would be most appropriate for Mars. But since in timekeeping the unit of a second is not used on Mars, all scientific units derived therefrom such as meters per second, kilometers per hour, newtons, watts and relationships between Martian units have to be developed precisely (see comparison of Earth and Mars data).
 

What we attain is a simple and uncomplicated Martian system:
o   Years are counted in ORBs
o   Days are counted in SOLs
o   Seasons stretch over four groups of sols differing north and south of the        equator  ( 194,176,142,156 sols)
o   Hours are counted in CENTISOLs, 100 centisols per sol (exactly 100.00089)
o   MILLISOLs are added for precision
o   Surface coordinates are described in MERs and LATs
     100 mers around Mars’ equator, and + 25 LATs and - 25 Lats to north and south
o   10 local time zones can be used in addition to Mars Zero Time
o   Since 100 meridians are passed during 100 centisols at each of Mars’ rotation around its axis, there is an intimate relationship between space and time on Mars: the sun would be in its zenith at meridian 38 at 38 centisols time and at meridian 85 at 85 centisols time.
o   An event at the 38 meridian can be determined by using the “40-Local Time”
o   Temperatures would be measured in degrees Kelvin
o   The international scientific community could decide at what date this new
system could be started. Since we are in the beginning phase of Martian involvement, NOW is the time.
 
 

 

Unit:	Earth:	Mars:
Time	2 years 2 x 365 days 4 seasons 24 hours	1 orb 668/669 sols 4 seasons 1 sol
Time	1 hour 1/2 hour 15 minutes 1 minute  1 second	100 centisols 4 centisols 2 centisol 69 millisols 1 millisol
Distances	360º longtitude 90º latitude  1 meter	100 mers 25 lats 1 meter
Speed	1 km / hour 1 km / sec 1 m / sec	1 km / 4 centisols 1 km / millisol 1 m / millisol

MARTIAN CLOCKS
The need for a Martian clock
Scientists working on Martian projects need a system that compares Earth and Martian time data. Today watch manufacturers produce simple wrist watches as time pieces with many modes in which two modes can easily be exchanged which describe the specific situation on Mars (Ref. 3). We see Earth time in years, months, days, hours, minutes and seconds. Greenwich Mean Time is shown in another mode. Local time zones can be switched and daylight saving time can be turned on. Instead of using modes for Telememo, Schedule memo, calculators, alarm modes and stopwatch modes, two Martian modes could run parallel to the Earth timekeeping system.
Wouldn’t it be comfortable if every engineer and scientist could use a wrist watch besides the wall clocks in the main research office centers? Whenever a scientist wants to compare Earth with Martian time he simply presses a button to switch to another mode and can read immediately the Martian data for the same moment in Earth time. Since timekeeping and mapping systems for Mars are combined in my proposal it is easy to imagine the situation on a certain spot on Mars at a specific time. Data extending over 100 years can be calculated and preprogrammed by the clock manufacturer in collaboration with the scientific community to reflect practical and functional information.

Clock Data
The following data could be shown on the screen of the clock for the Martian timekeeping mode:
1.   The number of ORBs are shown in the upper left corner with two digits (see Figure 1). After each completed Mars orbit this number will be increased by one unit. It  can be increased to three digits as soon as the first 99 orbs have passed. At that time there will be no Y2K problems.
2.   The numbers designating the SOLs are shown by three digits in the upper right corner. They show the observer the actual sol being increased after every completed rotation of  the planet around its axis by one unit to 668 sols for each Martian orb. Since exactly 668.5990 sols make an orb, leap orbs with 669 sols can be computed in advance and included in the programmed sols.
3.   The seasons on the Red Planet are indicated by two sets of small windows. Distinctive and varying color filters could show green for the spring season, yellow for summer, brown for autumn and blue for winter. The colors bestow an immediate comprehension for the current seasons on the far away Red Planet which are divergent on the opposing sides of  the equator.
4.   Martian time is indicated on the clock’s lower left corner of the screen. Since 100 CENTISOLs make a complete sol, being counted from noon, the numbers from 0 to 99 show the observer the time of the Martian day. Numbers of 0 to 25 indicate the afternoon time, numbers from 25 to 75 indicate the night, and numbers from 75 to 99 the morning to noon time.
5.   By pressing the “time” button additional digits can be shown allowing more precise time determination with millisols. For example:  76.450 sols would be a precise moment of an early morning. Since each sol’s time is subdivided into 100 centisols for each rotation of the planet around its axis during which its 100 meridians are facing the sun, there is an intimate relationship between time and space. At the time of 23 centisols we know that the sun is at its zenith at this moment at meridian 23 and is so for each meridian at the identical time. A factor of 1.00089 is used when programming the watch to precisely determine the time of each centisol.
6.   Since projects occur at varying locations on Mars, special local time zones can be preprogrammed. There are different time zones on Mars similar to Greenwich Mean Time and numerous time zones on Earth. By holding down the “zone” button, ten local time zones can be viewed to reflect Martian times at different locations. The number of the selected time zone is displayed in the right lower corner of the clock’s screen.
7.   By pressing the “mode” button the second proposed mode will be displayed which is a beneficial feature for scientists working on Martian projects (see Figure 2). The screen reflects the positions of Mars and Earth on their different orbits around the sun. The sun is illustrated by a yellow dot in the center of the clock’s screen. The location of Mars is shown by a lit mark on the outer orbit, the position of Earth by a lit dot on the inner orbit. The positions of the planets have been calculated and preprogrammed by the clock manufacturer into the electronic system. The scientist instantly sees the location of the two planets in the solar system and discerns the time lapse interval of messages between the two planets which have been precalculated by the clock manufacturer for the different positions and are included in the clock’s elctronic system.The clock exhibits two numbers: the time needed for the messages streaming at light speed between the two planets in minutes and centisol figures. An alarm alerts the scientist of incoming messages for prompt action.
8.    The overall arrangement of the features shown in different locations of the Martian clock instantly informs the observer of important time elements thereby providing an easy and uncomplicated method of  keeping abreast of ongoing Martian projects.
9.   The costs for a Martian clock will be high in the beginning since the number of clocks produced will be relatively low. It may become less if the same timekeeping and mapping system is also applied for other spacial bodies in our solar system.
 

COMPARISON AND PRACTICAL USE OF CALENDARS

Planning of research events
The existence of a Martian timekeeping and mapping system makes practical sense when a method is developed to use it in cooperation with our Earth calendar for everyday planning of projects. Several clocks will be used at the wall of a research center showing besides Greenwich and local Earth times Martian data as described above. Time and local data can be marked on data printouts and photographs as done now by computers. A certain date can be set for the Earth time in the past or in the future and after pressing a button the corresponding Martian calendar time can be shown.
Since the proposed timekeeping and mapping system for Mars is simple and based solely on numbers for orbs, sols, centisols and millisols I envision two clock computers running parallel to each other. Today’s technology in timekeeping systems is so advanced that it can easily be accomplished. A clock can be programmed by the clock manufacturer that a certain Earth time can be set and at pressing a button, the corresponding Martian time could be shown.
 

Commencement of the two calendars
The scientific community would determine the point of time at which the Martian clock computer will be started to establish the Martian time: 0 orb, 0 sol, and 0 centisol. The inauguration shall correspond with a specific time of  the Earth timekeeping system which may be January 1, 2000 at noon or the moment of an important astronomical situation such as an equinox.
Clock manufacturers, computer programmers, astronomers, engineers and researchers could make a strong effort and work together to establish the calculated data and program the software, readily feasible with today’s technology.

References
1. Thomas Gangale, “ Mare Chronium, a short history of Martian          timekeeping” (AAS 90-287), The Case for Mars IV.
2. Dr.Robert Zubrin, “A Calendar for Mars” (Ad Astra, Nov/Dec.93)
3. Casio, User’s Guide for Module No.1478 wrist watch. Casio Inc.
Midlothian, VI. 23112.