Tithi

In Vedic timekeeping, a tithi is a [duration of two faces of moon that is observed from earth], or the time it takes for the longitudinal angle between the Moon and the Sun to increase by 12°. In other words, a tithi is a time-duration between the consecutive epochs that correspond to when the longitudinal-angle between sun and moon is an integer multiple of 12°. Tithis begin at varying times of day and vary in duration from approximately 19 to approximately 26 hours. Find Out Today's Tithi.
Panchanga.
A Hindu "muhurta" (forty-eight minute duration) can be represented in five attributes of Hindu astronomy namely, "vara" the weekday, "tithi", "nakshatra" the Moon's asterism, "yoga" the angular relationship between Sun and Moon and "karana" half of tithi.
"Tithi" plays an important role along with "nakshatra" in Hindus' daily as well as special activities in selecting the "muhurta". There are auspicious "tithis" as well as inauspicious "tithis", each considered more propitious for some purposes than for other.
There are 30 "tithis" in each lunar month, named as: