Janmasthami, or more popularly known as Krishna Janmashtami is the birthday of Lord Krishna which is celebrated with great fervor and zeal in India during the monsoon month. If we go by the Hindu calendar, this important day falls on the Ashtami or eighth day of the Krishna Paksh or dark fortnight of Bhadon month. No one actually knows when this festival originated! May be a thousand years back this festival found its foothold in our culture. One would actually come across various legendary stories and myths encircling the birth of Janmashtami.
Among all of them, the most widely accepted view is that Lord Krishna is the eighth incarnate of Lord Vishnu. We all have known from Mahabharata that the birth of Lord Krishna happened to kill the demon Kansa who happens to be his maternal uncle. Whenever there is some imbalance in the universe regarding peace and prosperity, it is said that Lord Vishnu comes to save the humanity from the hands of demons and goons.
Historians and scholars say that Lord Krishna took birth in a cellular jail in Dwapar Yug biologically to Vasudeva and Devaki. But Vasudeva had to cross the Yamuna River in a stormy night to pass on his child to a friend so save the child from the evil hands of Kansa. So, technically, Maiya Yashodha and Nanda of Gokul region of Mathura were the foster parents of Lord Krishna.
Now this Lord Krishna was a wonder child and his skills were noticed since childhood only. People started believing that this small boy named Krishna is among the commoners to save them from all tumultuous situations. Slowly, people of Nandgaon started celebrating the birth of Krishna in a grand way as they believed this day to be a fortunate one.
We can say that this festival initially originated in Gokul and slowly engulfed the Mathura region and later on the whole Uttar Pradesh state, India. And now even after 1000 years, the whole country celebrates the birth of Lord Krishna as he is the epitome of love, faith, friendship, and peace.