Janmashtami is the appearance day of Lord Shri Krishna, and the day is also called Gokulastami. Krishna appeared on the earth to free all evils and spread the proper knowledge in the world. The appearance day of Lord Krishna, who the Vedic scriptures describe as the Supreme Lord, in this material world is celebrated as Janmashtsmi.
Bhagavad-Gita Mentions,
"Janma karma ca me divyam evam yo vetti tattvatah"
The Lord's appearance is not like that of an ordinary man, who is forced to accept a material body. He appears out of His own sweet will. At the time of Krishna's appearance, the planetary systems were automatically adjusted so that everything became auspicious. Everywhere, there was an atmosphere of peace and prosperity. Auspicious stars were visible in the sky.