Halakhah su Salmi 135:7

I will now discuss the beginning of the year. I say, firstly, that a circle has no starting point. Rather it is at each person’s discretion. Thus the beginning of each individual’s year is from the moment he was born, and when the sun returns to the same point at which it was earlier, the person completes one full year.⁶⁹ It appears that Ibn Ezra is of the opinion that a person’s birthdate and age are determined by the solar calendar. This is in agreement with Rabbi Saadia Gaon’s statement: “A person’s life is numbered according to solar years, as is the life of any growing thing, for example, trees and the like” (Rabbi Saadia Gaon, Commentary on Genesis, p. 342). The starting point for correcting the sun’s orbit is from its apogee.⁷⁰ In calculating the true position of the sun relative to the zodiacal sphere, the starting point is the sun’s apogee. The angular distance of the sun’s mean position from the apogee is called the “mean anomaly”. (See Almagest iii, 8, p. 169.) The correction for a planet begins with the moment it is in conjunction with the sun, for then the planet is at the farthest point of its epicycle.⁷¹ The apogee of a planet relative to earth is always near the point of the planet’s conjunction with the sun, for then the centers of the earth, the sun, and the planet are collinear. Also the moon is at its farthest point of its deferent.⁷² Extreme values for apogee and perigee distances of the moon relative to earth occur when the moon passes those points close to full moon or new moon. (See Inconstant Moon by John Walker, p. 2.) However, these beginnings are not needed by all people.