According to the Hindu calendar, July 16, marks the Sun's transition into the Karka Rashi (Cancer); known as Karka Sankranti. This marks the beginning of Dakshinayana, the six months in which the Sun is traveling southwards and the end of Makar Sankranti- the six-month Uttarayana, Sun's northward journey. Makar Sankranti marks the transition of the Sun into Makara Rashi (Capricorn). Among all Sankranti, Makar Sankranti is the most significant one, and it is observed throughout India.
Transmigration of the Sun from one Rashi (zodiac) to the next zodiac is know as Sankranti. There are 12 Sankrantis in a year. All twelve Sankranti are divided into four categories:
Ayan Sankranti (Makar Sankranti and Karka Sankranti)
Vishuva or Sampat Sankranti (Mesha Sankranti and Tula Sankranti)
Vishnupadi Sankranti (Simha Sankranti, Kumbha Sankranti, Vrishabha Sankranti and Vrischika Sankranti)
Shadshitimukhi Sankranti (Meena Sankranti, Kanya Sankranti, Mithuna Sankranti and Dhanu Sankranti)
The southward journey of the Sun is associated with Yama, the god of death. Therefore, the southward movement is considered less auspicious that the northward movement. It is believed that the Gods go to sleep during the Dakshinayana phase of six months. Lord Vishnu is worshipped on the day of Karka Sankranti, and devotees observe fast donate food and clothes on this day. On Karka Sankranti, the Sun God is also worshipped along with Lord Vishnu, for health and prosperity. It is believed that one should avoid auspicious ceremonies, starting anything new or, as the day is not very auspicious, but is considered suitable for charity purposes.
According to western astrology, Karka Sankranti or the Sun's transition into the Cancer zodiac happens during the summer solstice (around June 21). And in the Indian context, it occurs around mid-July. This difference of timing arises due to different ways in with the two systems calculate the beginning of the astrological year.
According to Vedic Astrology, the beginning of the year is based on the position of the Sun with regard to fixed stars. However, in Western Astrology, the beginning of the year is based on Sun's position in relation to Earth that happens during the vernal equinox (around March 21).
Makar Sankranti marks the transition of the Sun into Makara Rashi (Capricorn) and the beginning of the six months of Uttarayana.
Mesha Sankranti marks the beginning of the New Year, according to the Hindu Solar Calendar. On this day, the Sun enters the Mesha Rashi (Aries zodiac). It generally falls on 14/15 April, and regional New Year festivals are celebrated on this day.
Mithuna Sankranti is celebrated as an annual menstruating phase of Mother Earth.
Dhanu Sankranti is celebrated as the first day of the solar month.
Karka Sankranti marks the transition of the Sun into Karka Rashi (Cancer). It also marks the end of the six-month Uttarayana period of the Hindu calendar and the beginning of Dakshinayana.