Arean calendar

The Martian Calendar is a distant variant of the Darian Calendar adopted in the early 22nd century, with some notable differences.

Mechanics

The Martian epoch begins as with the Darian Calendar, on March 11th, 1609 Earth (Gregorian) time, Midnight GMT, as 'year 0'.

Timekeeping on Mars makes use of the 'extended second', which is 1.027491251041666... seconds long. This preserves a 24-hour 'sol'. Typically, many use the terms 'second', 'minute', 'hour', 'day', 'week', and 'month' interchangibly, though when accuracy is noted, standard seconds are assumed.

Sol

A day on Mars is sometimes called a sol, primarily to differentiate it from the term 'day' on Earth. Because of the extended second, a Martian day still has 24 hours, each with sixty minutes, each with sixty seconds.

In Earth time, a sol averages 24 hours, 39 minutes and 35.24409 seconds long over the course of a tropical year, or 88775.24409 seconds. This creates some difficulty, since it is close enough to be conveniently considered a day yet not close enough for very accurate tracking.

Month

Each month is divided into four weeks of seven days, totalling 28 days per month, every month.

The weekdays are named in order: Helisol, Phobosol, Deimosol, Venusol, Terrasol, Jovesol and Lunasol, named after seven of the most brilliant planetary objects seen from the planet's surface (Saturn is omitted to avoid confusion with Saturday). As Phobos and Deimos are consumed in the voracious appetite of human industry, their memory will at least be aided by such naming.

Year

As with the Darian and Gregorian Calendars, the Martian Calendar uses the vernal equinox year. For Mars, this is roughly 668.5907 sols.

A year normally has 24 months. On several cycles, the last month of the year is dropped from the calendar. The most frequent 'drop year' occurs every 10th Martian year. The next drop cycle occurs every 25th and 75th years in a century. The final cycle occurs every 588th year, beginning with year 589, and assuming human civilization lasts so long, on those years which would cause two months to be dropped, the dropped month is pushed to the next year instead.

Usage

The development of satmets allow for near-instantaneous communication between Earth, Luna, Mars, and Ouranos Prime, and with further plans to incorporate such transmitters into the stellar gates. This has made the Helios Calendar significantly more popular, and general usage of the Gregorian and Martian Calendar has fallen significantly.

Still, it is extremely useful for local needs, and millions of people never have to use anything else to conduct daily business. It is first and formost a social calendar, and serves as such.

Most call a day a day, only referring to a sol as a unit of time when being specific or discussing matters with residents of Earth or Luna.