Hanuman Jayanti is wrongly celebrated on Chaitra Poornima. Actual date (tithi) should be Poorvabhadra nakshatra in the month of Vaisakha.
Parasara Samhita, the only authentic book on Hanuman clearly states that Hanuman was born in 2nd half (krishna paksha) of Vaisakha maasa when Moon was in Poorvabhadra nakshatra and on a Saturday morning.
Usually this date fall in late May or sometimes early June. In 2023 it is on 14 May.
The date which most of north India assumes wrongly as Hanuman Jayanti (early April) is the day when Hanuman found seetha in Lanka and this is to celebrated as Hanumad Vijayam (his victory - the day when he met seetha and burned Lanka)
