Common Festival Date

Pradhosha Pooja for Siva falls on the evening of 13th day or thrayodhasi of each lunar cycle (waxing and waning) in a month (the 13th day would depend on the extent of the thithi). Nrisimha pooja is also done on Prodhosham, since the Lord Narayana killed Hinranya Kasipu in the Pradhosham Kaalam.

Both events relating to Siva and Vishnu signify protection of the worlds from deadly hazards like deadly Poison and invincible Demon. Some scholars like to look at the episodes in symbolic sense of the elimination of the dangers from Karma Malam that chases us as Destiny (represented by Poison) and Ignorance or Ego (represented by the evil demon) that goads us toward illusion.

Some even argue that Sriman Narayana got the ferocity of Destruction from Siva thatwam to kill the invincible demon. The ferocity or Ugram was taken back by Shiva at the close of the drama. Just like Vishnu Thatwa intercedes in problems of Siva thatwa (as in Bhasmasura episode), Siva thatwa also intercedes in the problems of Ministry of Vishnu. They can be described as the Knowledge (Budhi) and strategy (Yukthi) in us, each inter dependent but appearing as mutually exclusive!