Someshwar Puja is observed during the Shukla Paksha of Shravan month as per traditional Hindu lunar calendar followed in North India. Someshwar form of Shiva is worshipped during the puja. Information regarding this puja is found in the Narad Puran. Some devotees observe a vrat on the occasion.
The puja and vrat is associated with Shiva rescuing moon (Chandra or som) and giving refuge to him in his matted locks.
Those observing the vrat wake up early morning, take bath, and perform puja to Shiva by making clay Shivling. Only vegetarian food is eaten on the day. White colored Prasad is prepared and offered in the evening.
The fast is observed for three months on all Mondays during Shukla paksha or waxing phase of moon.
It is believed that on successful completion of the vrat, a devotee will be blessed with knowledge, health and wealth.