Tithi
Trayodashi Meaning
Trayodashi is the thirteenth lunar day, important for Pradosh Vrat. In panchang, tithi is calculated from the angular distance between the Sun and Moon, so its start and end time can vary by location.
In Simple Terms
Trayodashi is the thirteenth lunar day, important for Pradosh Vrat. Its exact use depends on the wider panchang context: tithi, nakshatra, yoga, karana, vaara, and local sunrise.