Pradosha Vrat Puja is an auspicious day devoted to Lord Shiva. It falls on the 3 day of every lunar fortnight in traditional Hindu calendar. Shiva devotees fast from sunrise to sunset and important rituals and pujas are held during the twilight period.
Pradosh vrit means the dusk of the early night or evening tide. The best time to worship of Lord Shiva is the sun sets and the night approaches.
According to Skanda Purana, this Pradosh Puja is particularly auspicious. An excellent opportunity to seek long life (deergha aus), success, health, peace (shanti & prosperity (pushti) from Siva & Parvati.