A tithi is a lunar day. It is the time taken by the Moon to travel 12 degrees in the sky. Due to the relative motion of the Sun and the Moon, the length of a tithi can vary from 21.5 hours to up to 24 hours. There are 30 tithis in a lunar month including Poornima and Amavasya. The tithis are divided into Shukla Paksha tithis and Krishna Paksha tithis, with 15 tithis making for each Paksha.
The tithis indicated by the Tithi calculator are:
Krishna Paksha tithis
Shukla Paksha tithis
The Moon represents emotions in Vedic astrology. In many cultures, the Moon is given more importance than the Sun, and the Moon calendar is followed while deciding day-to-day activities. The movement of the Moon in the heavens results in 30 tithis, including Poornima and Amavasya in a lunar month. Each tithi is identified by the shape of the Moon that is visible in the sky on that day.
The Tithis are further divided into five - Nanda, Bhadra, Jaya, Rikta, and Poorna.
Apart from these five, there is also Suniya Tithi which is not suited to carry out any kind of work.
The Suniya Tithis are as follows - Chaitra Krishna Ashtami, Vaishakh Krishna Navami, Jyestha Krishna Chaturdashi, Jyeshtha Shukla Trayodashi, Ashada Krishna Shashthi, Shravan Krishna Dwitiya and Tritiya, Bhadrapada Krishna Pratipada and Dwitiya, Ashwin Krishna Dashami and Ekadashi, Kartik Krishna Panchami and Shukla Chaturdashi, Aghan Krishna Saptami, and Ashtami, Paush Krishna Chaturthi and Panchami, Magh Krishna Panchami, and Magh Shukla Tritiya.
Krishna Paksha or the waning phase is the fortnight between the Full Moon (Poornima) and the New Moon (Amavasya). There are fifteen tithis in Krishna Paksha.
The Shukla Paksha or the Waxing Phase is the fortnight from New Moon (Amavasya) to the Full Moon (Poornima). There are fifteen tithis in the Shukla Paksha.
The birth Tithi can be calculated using date, time, and place of birth. An individual's birth tithi has a lot of influence on his/her life and personality. The Tithi should never be overlooked when identifying auspicious and inauspicious muhurats.