The birth anniversary of Lord Hanuman is celebrated on the day of Chaitra Purnima. Apart from this, Hanuman Janmotsav is also celebrated on Chaturdashi of Krishna Paksha of Kartik month. Hanuman Janmotsav will be celebrated on 23rd April this year. Hanuman Jayanti is celebrated twice every year. In Kerala and Tamil Nadu, there is a tradition of celebrating Hanuman Jayanti on the new moon day of Margashirsha month and in Orissa on the first day of Vaishakh month.
One birth anniversary of Hanumanji is celebrated as his birth anniversary and the other birth anniversary is celebrated as Vijay Abhinandan Mahotsav. Hanumanji had amazing powers since birth. Once he mistook the sun for a fruit and tried to eat it. To stop the Sun God from eating it as a fruit, Lord Indra attacked Hanumanji and made him unconscious.
According to religious belief, Hanumanji is considered the son of wind. Due to this incident Pawandev became angry and stopped the flow of air. After this there was a crisis in the entire universe. After all the gods and goddesses prayed to Vayudev, Lord Brahma gave second life to Pawan's son and all the gods gave him their powers. The day Hanumanji got second life was the full moon day of Chaitra month. Therefore Hanuman Jayanti is celebrated on this date.
It is believed that on the Chaturdashi date of Krishna Paksha of Kartik month, Mother Sita had blessed Hanumanji with immortality. Therefore Hanuman Jayanti is also celebrated on this day. Apart from this, in Valmiki Ramayana, the date of birth of Hanumanji is stated to be Chaturdashi of Krishna Paksha of Kartak month. Therefore Hanuman Jayanti is also celebrated on this day. Apart from this, in Valmiki Ramayana, the date of birth of Hanumanji is stated to be Chaturdashi of Krishna Paksha of Kartak month.