Hanumath Jayanthi was celebrated on Chitra Pournami Day (April 19th 2008).  This is the day it is beleived that our ANJU's Garbha Pravesam taken place.  Jananam is beleived to be on Marghazhi Ammavasai(Usually comes in December/January). 

 In India people Celebrate Hanumath Jayanthi during different periods. 

People in Tamil Nadu Celebrate during Marghazhi (Tamil Month) It comes in either December / January (Marghazi Moolam Amavasai Dhinam)

People in Andhra Celebrate during Chithirai (Tamil Month).  It comes in April. (Chitra Pournami) (Maruthiyim Amsam by Sri Smartha Ramadasan)

People in North India Celebrate on Vaikasi Masam (Tamil Month), Krishna Paksham, Dhasami Saturday, Pooratathi Nakshatram (Hanumath Ashtakam)