On July 16, the Sun will once again enter Cancer sun sign making an effect on the personal and professional life of the people. This day is called Karka (Cancer) Sankranti. According to the Hindu calendar, Cancer solstice is considered the end of the six-month Uttarayan period. With this, Dakshinayan begins which continues till Makar Sankranti. Pitru Darpan, charity, dharma and bath are very important on the day of Sankranti. This day is celebrated with pomp in many places in India. However, no auspicious work is done as soon as the Sun marks a transition into the Cancer zodiac. It is believed that at this time the blessings of Gods are not given for auspicious work.

source https://www.indiatvnews.com/lifestyle/news-karka-sankranti-2020-date-shubh-muhurat-for-puja-know-why-doing-auspicious-work-is-forbidden-on-this-day-632619