excerpt from

The Man Who Conquered Mars

by Doug Turnbull

2010

edited by Thomas Gangale

In listening to the exchange, Ana noted that Bob had only been on Mars for a year. When he told her that he had been here for two years, he had been using the Earth calendar. He needs to get on local time, she thought. Local time meant the Mars Clock and calendar, which were used in everyday commerce. While not used in scientific matters where Earth measurements prevailed out of convenience of communication and custom, Mars time was more relevant to the actual phenomena the units were describing. Earth days were shorter than Mars days, and using Earth hours and minutes to refer to a Mars day would make a day 24 hours and 39 minutes long. In matters of business and government, Mars Colonists used the Earth calendar for purposes of determining the official date, but for their own daily use, the Mars calendar prevailed. This was similar to the widespread practice on Earth of using local measurements, such as the English system, for day-to-day living while using the more widely accepted metric system in science and industry, or of Japan retaining its traditional method of measuring the years while also adopting Western forms of date keeping for military and economic purposes. Like various Earth-side calendars, Mars' calendar was part science and part convention. The Mars calendar year consisted of 669 sols, or days, divided into four seasons, which have their basis in the natural planetary phenomena of axial tilt and Mars orbital eccentricity. While large swings in temperature related to the seasons are characteristic of the northern and southern regions of the planet, there is little seasonally related temperature variation near the equator, which was one of the reasons for locating Mars Colony there. Another reason was that Mars' equatorial zone is warmer on average, just like Earth's.