Pradosha

Pradosha or Pradosham (IAST: Pradoṣa) is a bimonthly occasion on the thirteenth day of every fortnight in Hindu calendar. It is closely connected with the worship of Hindu god Shiva. The auspicious 3 hour period, 1.5 hours before and after the sunset is one of the optimum time for worship of Lord Shiva. The fast or vow performed during the period is called "Pradosha vrata". A devotee should wear rudraksha, Vibhuti and worship Lord Shiva by Abisheka, Sandal paste, Bilva leaves, Fragrance, Deepa & Naivaedyaas (Food offerings)

Etymology

Pradosha is indicative of day names in the calendar. Etymology of Pradosha - Pradosha is the son of Kalpa and Dosha. He had two brothers namely Nishita and Vyustha. The three names mean beginning, middle and end of night. The days from new moon day to full moon day is called "Sukla Paksha" and days from every full moon day to new moon day is called "Krishna paksha". During every month and during every paksha, the point of time when triyodashi (13th day of the fortnight) meets the end of dwadasi (12th day of fortnight) is called Pradosha. During pradosha, Nandi (the sacred bull of Shiva) in all the Shiva temples in South India is worshipped. The festival idol of Shiva with Parvathi in a seated pose on Nandi is taken as a procession in the temple complex.