Maha Pradosh is a rare occurrence of the Pradosham, or Pradsha Vrata, dedicated to Lord Shiva falling on a Saturday during the waning phase of moon in a traditional Hindu lunar calendar. The Pradosh period – the twilight period – on the 13th day during Krishna Paksha (waning phase of period) is considered highly auspicious for worshiping Lord Shiva and Goddess Parvati.
Fasting from sunrise to sunset is the main ritual on the day for Shiva devotees.
The prayers and rituals for Pradosh begin around 1.5 hours before sunset and end one hour after sunset.
Special pujas are performed in Shiva temples during the period. It is said that Lord Shiva and Parvati are in a happy mood during Pradosham period and are easily pleased.
Pradosh falling on Saturday is known as Shani Pradosh. But the Pradosh falling during Shukla Paksha (waxing phase of moon) is not defined a particular name but is also considered auspicious by many.