Wikipedia
Pradosha
Pradosha or Pradosham (IAST: Pradoá¹£a) 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, Vilva leaves, Fragrance, Deepa & Naivaedyaas (Food offerings)