Sita Navami or Janaki Navami, also known as Sita Jayanti, is celebrated as the birth anniversary of Goddess Sita. On this day, married women observe fast and pray to the Goddess for long life of their husbands.
Sita Jayanti is observed on Shukla Paksha Navami of Vaishakha month. Sita, who was born in Pushya Nakshatra on Shukla Paksha Navami of Vaishakha month was married to Lord Rama who was born on Shukla Paksha Navami of Chaitra month. Hence as per Hindu calendar, Sita Jayanti falls one month after Rama Navami.
Sita was the adopted daughter of King Janaka of Mithila and hence Sita was also known as Janaki. Hence Sita Navami is also known as Janaki Navami. It is believed that when King Janaka got Sita when he was ploughing his land to perform a Yajna. He found a baby girl in a Golden casket inside the field. A ploughed land is referred as “Sita” and hence the King named the baby girl as Sita.