Solar longitude ( the ecliptic longitude of the sun ) in effect describes the position of the earth in its orbit , being zero at the moment of the vernal equinox. Since it is based on how far the earth has moved in its orbit since the equinox, it is a measure of what time of the tropical year (the year of seasons) we are in, but without the inaccuracies of a calendar date, which is perturbed by leap years and calendar imperfections.  Solar longitude    is especially used in the field of meteor showers, because a particular meteor shower is caused by a stream of small particles very close to the elliptical orbit of a comet, or former comet. This means that the shower occurs when the earth reaches a particular point in its own orbit, designated by the solar longitude. Solar longitude can also be used for other planets, such as Mars . This gives a way of saying what time of year it is on that planet. Solar longitude does not increase linearly with time, the deviation being larger the greater the eccentricity of the orbit. For instance, here are the dates for multiples of 90° solar longitude on Mars in the mid 1950s: + solar longitude date time (Earth days) 0° 11 April 1955 199 90° 27 October 1955 183 180° 27 April 1956 147 270° 21 September 1956 158 0° 26 February 1957 687 The Martian year is divided into 12 Martian months of unequal duration, with the breakpoints being at solar longitudes that are multiples of 30°. See also Martian calendar
Solar longitude , commonly abbreviated as Ls, is the ecliptic longitude of the sun , i.e. the position of the sun on the celestial sphere along the ecliptic. It is also an effective measure of the position of the earth (or any other sun-orbiting body) in its orbit around the sun, usually taken as zero at the moment of the vernal equinox. Since it is based on how far the earth has moved in its orbit since the equinox, it is a measure of what time of the tropical year (the year of seasons) we are in, but without the inaccuracies of a calendar date, which is perturbed by leap years and calendar imperfections. Its indepence from a calendar also allows it to be used to tell the time of year on other planets, such as Mars. Solar longitude does not increase linearly with time, the deviation being larger the greater the eccentricity of the orbit. For instance, here are the dates for multiples of 90° solar longitude on Mars in the mid 1950s: + solar longitude date time (Earth days) 0° 11 April 1955 199 90° 27 October 1955 183 180° 27 April 1956 147 270° 21 September 1956 158 0° 26 February 1957 687 Of meteor showers Solar longitude is especially used in the field of meteor showers, because a particular meteor shower is caused by a stream of small particles very close to the elliptical orbit of a comet, or former comet. This means that the shower occurs when the earth reaches a particular point in its own orbit, designated by the solar longitude. Of Mars The Martian year can be divided into 12 Martian months of unequal duration, with the breakpoints being at solar longitudes that are multiples of 30°. 
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(
, commonly abbreviated as Ls, is
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, i.e.
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earth
sun on the celestial sphere along the ecliptic. It is also an effective measure of the position of the earth (or any other sun-orbiting body)
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, being
around the sun, usually taken as
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Its indepence from a calendar also allows it to be used to tell the time of year on other planets, such as Mars.
A
does not increase linearly with time, the deviation being larger the greater the eccentricity of the orbit. For instance, here are the dates for multiples of 90° solar longitude on Mars in the mid 1950s:
A
+ solar longitude date time (Earth days) 0° 11 April 1955 199 90° 27 October 1955 183 180° 27 April 1956 147 270° 21 September 1956 158 0° 26 February 1957 687
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Of meteor showers Solar longitude
R
Solar longitude can also be used for other planets, such as Mars . This gives a way of saying what time of year it is on that planet.
Of Mars
D
Solar longitude does not increase linearly with time, the deviation being larger the greater the eccentricity of the orbit. For instance, here are the dates for multiples of 90° solar longitude on Mars in the mid 1950s:
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+ solar longitude date time (Earth days) 0° 11 April 1955 199 90° 27 October 1955 183 180° 27 April 1956 147 270° 21 September 1956 158 0° 26 February 1957 687
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is
can be
D
See also Martian calendar