On lunar calendars there are 13 moonths per year, since it takes the moon about 27 days to orbit the earth. 365/27 = 13.5. This makes lunar calendars slightly awkward. So we reduced the number of months by making them three to four days longer, twelve months per solar year.
http://www.answers.com/Q/How_many_days_are_in_a_Martian_month
Another consideration in designing a calendar is accounting for the fractional number of days in a year. Earth’s year is 365.24219 days long, and so calendar years contain either 365 or 366 days accordingly. Such a formula would need to be developed to account for the 668.5921-sol Martian year. All of that may make you wonder why a Martian calender would ever be necessary. There is an earnest push to put man on Mars.
http://www.universetoday.com/14718/how-long-is-a-year-on-mars/
So the Martian year consists of 668.6 Martian days.   A Martian day is 39.5 minutes longer than an Earth day. But Mars' circumference is just over half of Earth's, so its spin velocity is also about half, just 868 km/hr compared to Earth's 1674 km/hr at the Equator. 8 people found this useful.
http://www.answers.com/Q/How_many_days_are_in_a_Martian_month
To easily find out how many days are in a specific month, just use this simple method: Every other month, starting with … January and ending with December, has 30 days in it.
http://www.answers.com/Q/How_many_days_are_in_a_Martian_month
Martian Year. For any planet, a year is the time it takes to make one orbit around the sun. Because Mars is farther away from the sun, it has to travel a greater distance around the sun. It takes Mars about twice as long as it does for Earth to make one circle around the sun. Therefore, a year on Mars lasts twice as long. Mars Seasons. Mars has four seasons, roughly twice as long as those on Earth, but with more variation given Mars' eccentric orbit and the fact its orbital speed varies more as result (fastest when at perihelion; slowest at aphelion).
http://mars.nasa.gov/allaboutmars/extreme/martianyear/
From this site, we learn that a Martian day is 88775.260726 seconds long, which is 24.659794646 hours, or 24 hours, 39 minutes, and 35.260726 seconds, or 1.027491443588 Earth days of 86,400 seconds each.
http://www.quadibloc.com/science/cal05.htm
40 minutes a day adds up to a whole day in 36 days, so the Martian week would come into step with the Earth week about once every 250 days. The Martian synodic period, the time when Mars, on average, comes into a given relationship with Earth, is about 780 days.
http://www.quadibloc.com/science/cal05.htm
These are the months in order and their number of days.   January - 31   February - 28 or 29 depending on whether it is a leap year or not.   March - 31  …  April - 30   May - 31   June - 30   July - 31   August - 31   September - 30   October - 31   November - 30   December - 31.
http://www.answers.com/Q/How_many_days_are_in_a_Martian_month
It lasts 686.98 Earth days or 1.88 Earth years. Now, given that a day(sol) on Mars is longer than on Earth, you would get a different answer. If you were standing on Mars, a year would take 668.5921 sols. In other words, Mars rotates 668.5921 during one orbit about the Sun.
http://www.universetoday.com/14718/how-long-is-a-year-on-mars/
Finally, twenty-four months would be 27.9 Martian days long. This would result in a neat and tidy division of the year into twelve equal parts; each one would be composed of two months.
http://www.quadibloc.com/science/cal05.htm
how many days are in a martian year?
There are 668.6 days in a Martian year. There are 668.6 days in a martian year.