How often does Christmas and the "New Year" on Mars?

The calendar of Mars is relevant, as we are going to master this planet. The colonists will have to live there according to the Martian days, considering the Martian seasons of the year (otherwise you will not organize field work), and, of course, celebrate the Martian New Year. The change of seasons on Earth is connected with the inclination of its axis of rotation to the plane of the orbit: six months the Earth is better at exposing the Sun to its Northern Hemisphere, and at this time we have summer, and half a year - Southern, and they have summer in Australia, and we have winter. It's the same on Mars. The axis of rotation of Mars (25.2 °) is inclined to the perpendicular to the plane of its orbit almost in the same way as at the Earth (23.4 °). It is the slope of the rotation axis of Mars that ensures the change of the seasons. True, there is no biosphere on the surface of Mars, that is, there is no spring flowering of plants and winter hibernation of animals. But the average daily temperature and snow cover in high latitudes and polar regions change quite strongly throughout the year, and strong seasonal winds blow.

The year on Mars lasts 687 terrestrial days, that is, about 669 Martian sunny days. The fact is that the day on Mars is about 40 minutes longer than the earth's; this period was called "sol". The aphelion of its orbit, that is, the most distant point from the Sun, Mars passes in the middle of the winter of the Southern Hemisphere. Therefore, the climate in the southern hemisphere is "sharply continental," that is, annual temperature fluctuations are very large. And in the Northern Hemisphere, for the same reason, the climate is milder. For example, summer in the Southern Hemisphere is 30 degrees warmer than in the North, and winter is almost as much colder. In principle, it's the same on Earth: during winter in the Northern Hemisphere, our planet is closer to the Sun, so it's not as cold as it could be.

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Extension of the orbit of Mars leads to large differences in the duration of seasons. Thus, northern spring and summer, taken together, last 371 sol, that is much more than half of the Martian year. At the same time, they fall on a portion of the orbit of Mars distant from the Sun. Therefore, on Mars the northern summer is long and cool, and the southern one is short and relatively warm. Although two small satellites revolve around Mars - Phobos and Deimos, their role in the night illumination of the planet is almost zero, so the monthly cycle on Mars could not be introduced. Nevertheless, for the convenience of future researchers of the Red Planet, they are offered a calendar containing 24 months to 28 sols each, grouped in 4 weeks, except for the last month of each quarter, in which one is less for one. This is one of the first Martian calendars developed by the American engineer Thomas Gangale and published by him in 1986. Later Gangale repeatedly modified his calendar.

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There were suggestions from other authors. But each of them faced the same problem as the creators of the Earth calendar - with an integral number of days a year. The Martian year lasts 668,5907 Martian days. Therefore, to accurately coordinate the diurnal and yearly cycles, Mars will also have to introduce a system of leap years, reminiscent of the earth in the first approximation, it will have a five-year cycle with three "full" years and two "shortened" ones.

In the history of the Earth, different peoples had many calendars (there are still a lot of them), and in each of them the beginning of the year was at its date. For us it is now common to celebrate the beginning of the year on January 1, but there were times when we celebrated the New Year on September 1 and at the end of March, on the day of the vernal equinox (in Iran, and now they do so). In the calendars of Mars, their creators are also often asked to consider the beginning of the year the moment of the Martian vernal equinox, that is, the beginning of the astronomical spring in the Northern Hemisphere of the Red Planet. If you agree with this, the next New Year on Mars will be May 5, 2017.

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But from which year to keep track of the years on Mars - in this issue there is no agreement yet. The years of the first soft landing on Mars, the first observation of Mars in a telescope, the first calculation of its orbit and so on were suggested. Of course, you can wait for the first people to land on Mars and start the count of years from the "small step of one person". But we really do not want to have negative years in the Martian calendar (before the advent of man), when our technology was already working there, and astronomers have been studying the Red Planet for several centuries. It seems reasonable to keep an account of the Martian years from the invention of the telescope (1609), because until that moment Mars was just an orange star in the sky, and the Galilean telescope turned it into a full-fledged planet.

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