Both Vat Purnima Vrat and Vat Savitri Vrat are similar celebrations observed in different names. Married women observe Vat Purnima Vrat for long life and well-being of their husband.
Festivals as per Amanta and Purnimanta lunar calendars usually occur on the same day. However, Vat Savitri Vrat may be taken as an exception.
Purnimanta calendar is followed in North Indian states, like Uttar Pradesh, Madhya Pradesh, Bihar, Punjab and Haryana. In the other states usually Amanta lunar calendar is followed.
As per Purnimanta calendar, Vat Savitri Vrat is observed on Jyeshtha Amavasya, which coincides with Shani Jayanti.
According to Amanta calendar Vat Savitri Vrat, also known as Vat Purnima Vrat, is observed on Jyeshtha Purnima.
Due to this difference, the married women in Maharashtra, Gujarat and southern Indian states observe Vat Purnima Vrat 15 days later than it is celebrated in North India. However, the legend behind the fast remains the same in both cases.
Legend says that Savitri tricked Lord Yama, the lord of death, by asking intelligent questions to Him that compelled him to return the life of her husband Satyawan. Hence married women observe Vat Purnima Vrat for the long life and well-being of their husband.