In the Hindu calendar or Panchang, tithi or thithi is a full lunar day or the time taken by the longitudinal angle between the sun and moon to increase by 12°. There are a total of 30 tithis in a month defined in Vedic Astrology.
The first fifteen tithis are included in Shukla Paksha whereas the next fifteen tithis are included in Krishna Paksha. With the inclination of moon at 12 degrees, completion of one tithi takes place in a month. Nanda, Bhadra, Rikta, Jaya and Poorna are the 5 subdivisions of tithi.
Tithis are considered to be of high importance in the Hindu calendar or Panchang as it provides the details of auspicious timings for people to undertake a new task. There are auspicious tithis as well as inauspicious tithis, each considered more propitious for some purposes than for others. Tithis begin at varying times of day and vary in duration from approximately 19 to 26 hours.
Tithis of the Hindu Panchang are divided into two parts – Shukla and Krishna Pakash. Each has a total of 15 tithis, collectively making a total of 30 tithis in the calendar.
Prathama / Padyami
Most suitable for any and all kinds of auspicious and religious ceremonies, the presiding deity of the first lunar day is Agni.
Dwitiya / Vidiya
Suitable for the laying of foundations for buildings and other things of a permanent nature, Vidhatr or Brahma rules the second lunar day.
Tritiya / Thadiya
Good for cutting of the hair, nails and shaving, Goddess Gauri is the lord of this day.
A day marked for the destruction of one's enemies, the removal of obstacles, and acts of combat as Yama/Ganapati is lord of the 4th lunar day.
Beneficial for undergoing surgery, administering medicine, the purging of poisons as the Naaga or Serpents rules this day.
A day made to celebrate special occasions or festivities, enjoyment, meeting new people and marking new friendships as Karttikeya presides over this day.
This day results favourable in order to begin a journey, buy conveyances, and deal with other such things of a movable nature as The 7th lunar day is ruled by Surya.
A day which results beneficial in building of one's defences, taking up arms and fortification as Rudra rules this day.
A day prone to embark acts of destruction, and violence. Inauspicious for ceremonies and journeys as Goddess Ambikaa rules this day.
Auspicious for acts of virtue, religious functions, spiritual practices, and other pious activities, this day is ruled by Dharmaraja.
One of the most auspicious days with special religious significance in Hinduism and Jainism, usually observed by fasting and devotional activities with remembrance of the Supreme Lord as Rudra rules this day.
Auspicious for religious ceremonies, the lighting of the sacred fire, and the performance of one's duties as God Vishnu rules this day.
A day for forming friendships, sensual pleasures, and festivities it is ruled by Kamadeva.
A day suitable for administering spiritual connect and calling of elementals and spirits as Goddess Kali rules this day.
Poornima (full moon) or Amavasya (new moon)
Poornima or full moon is ruled by Moon and is suitable for merry making and fire sacrifice and Amavasya or the New Moon is governed by Pitru-divas, suitable for the propitiation of the Manes and performance of severities.
A tithi is when the Moon completes its 12-degree movement of the Sun. Many festivals and rituals are associated with the Tithis with most falling either on Amavasya or Poornima. All Tithis occur twice a month except for Amavasya and Poornima, which occur just once every month.