tithis
Tithis are lunar days in the Hindu lunisolar calendar. A tithi is the time duration in which the longitudinal angle between the Sun and the Moon differs by 12 degrees. Since the Moon moves approximately 12 degrees per day relative to the Sun, a tithi is typically about 24 hours, but can be shorter or longer. There are thirty tithis in a lunar month, which is divided into two halves: Shukla Paksha (the waxing phase of the moon) and Krishna Paksha (the waning phase of the moon). Each paksha has fifteen tithis.
The names of the tithis are numbered from one to fourteen, followed by the Amavasya (new moon)