For a better living on Mars, the Calendar on Mars has been designed to fit into the Martian orbit.

Our Martian calendar is based on the Darian calendar. In general, there are 24 months on Mars. However, different culture has given the months different names. One of the most popular ones is the 24 solar terms used by Chinese. Each martian year starts with the Vernal or Spring Equinox on Mars. Each martian year is basically one solar year. Year 0 on Mars is 1970-04-28 on Earth.

The 24 months are distributed to 4 seasons. The first five months in the season have 28 martian days while the sixth month has 27 martian days. The last month of the leap year will add another day to the month.

Spring	Summer	Autumn	Winter
Lichun（Month 22）	Lixia（Month 4）	Liqiu（Month 10）	Lidong（Month 16）
Yushui（Month 23）	Xiaoman（Month 5）	Chushu（Month 11）	Xiaoxue（Month 17）
Jingzhe（Month 24）	Mangzhong（Month 6）	Bailu（Month 12）	Daxue（Month 18）
Chunfen（Month 1）	Xiazhi（Month 7）	Qiufen（Month 13）	Dongzhi（Month 19）
Qingming（Month 2）	Xiaoshu（Month 8）	Hanlu（Month 14）	Xiaohan（Month 20）
Guyu（Month 3）	Dashu（Month 9）	Shuangjiang（Month 15）	Dahan（Month 21）

As shown in the table, each season has 6 months.

There are 4 weeks in each months. What is different here on Mars is that the first day of the month is always sunday. Here is a typical month on Mars.

Sunday	Monday	Tuesday	Wednesday	Thursday	Friday	Saturday
1	2	3	4	5	6	7
8	9	10	11	12	13	14
15	16	17	18	19	20	21
22	23	24	25	26	27	28

Whether the last day of the year is a 28th depends the algorithm of the leap year. The leap year on Mars is quite similar to the leap year on Earth.

Each martian day is 39 min 35.244 seconds longer than earth day. Each martian year has 668.5907 martian days. To have an accurate calendar, leap years are added. In 10 years, there will be 6 years of 669-day-year (leap year), and 4 years of 668-day-year (common year). The leap years are the years that are even and are divisible by 10. However, if the year is divisible by 100, it is a common year. If the year is divisible by 1000, it is a leap year. If the year is divisible by 3000, it is a common year.

Some Important Days

To calibre the algorithm, we will have the four dates on Earth which corresponds to spring equinox, summer solstice, fall equinox, and winter solstice of the year 0 on Mars.

Spring Equinox	Summer Solstice	Fall Equinox	Winter Solstice
1970-04-28	1970-11-12	1971-5-15	1971-10-8

We also list some of the important days in martian calendar.

Martian Dates (Month-Day)	Name
1-1	Spring Equinox
6-12	Aphelion
7-27	Summer Solstice
14-11	Fall Equinox
18-12	Perihelion
19-14	Winter Solstice