Purattasi, one of the auspicious Tamil months, is dedicated to Lord Vishnu (Lord Venkateswara).

Purattasi masam is the month in which full moon normally occurs either on Poorattadhi/ Uttirattadhi stars.  Lord Vishnu devotees consider Purattasi as the ideal month for thanking the Lord for preserving the Universe at the end of Kali Yuga. Devotees gather in large numbers at Lord Vishnu temples and special prayers are offered.