Uttarayana

The term Uttarāyaṇa (commonly Uttarayanam) is derived from two different Sanskrit words – "uttaram" (North) and "ayanam" (movement) – thus indicating the northward movement of the Sun. In the Gregorian calendar, this pertains to the "actual movement of the sun with respect to the earth." It is also known as the six-month period that occurs between the winter solstice and the summer solstice (approximately 20 December - 20 June). According to the Indian solar calendar, it refers to the movement of the Sun through the zodiac. This difference occurs because the solstices continually precess at a rate of about 50 arcseconds per year due to the precession of the equinoxes, i.e. this difference is the difference between the sidereal and tropical zodiacs. The Surya Siddhanta bridges this difference by juxtaposing the four solstitial and equinoctial points with four of the twelve boundaries of the rashis.

The complement of Uttarayana is Dakshinayana (the southward movement of the Sun). It is the period between Karka Sankranti and Makara Sankranti as per the sidereal zodiac and between the summer solstice and winter solstice as per the tropical zodiac.