Aashaadh Maas is the 4th month of Hindu Lunar calendar year. The following Vrat and festivals fall in this month.

Poornimaa - Guru Poornimaa
Guru Poornimaa is not a festival as such, it is a kind of Vrat (fast) day to celebrate Guru's day. This is the day when people start their Chaaturmaasya Vrat for four months.