Krishna Janmashtami, Gokulashtami, Krishnashtami is celebrated by Hindus as the birthday or Lord Krishna. August 10 is celebrated as Janmashtami by Vaishnavas whereas Gokulashtami date for Smartha sect is on August 9 one day before the Krishnashtami celebrated by Vaishnavas.

Legend of Janmashtami
Mathura was led by Kansa a wicked king, who was also the uncle of Sri Krishna. He had a sister Devaki, who was married to Vasudeva. It was predicted that Sri Krishna would be born to Devaki and would kill the wicked king Kansa. This enraged Kansa and he had all the male child of Devaki killed, after imprisoning Devaki and Vasudeva. But since the eight avatar of Lord Vishnu was bound to kill Kansa, Sri Krishna was born in midnight. All the other children born to Devaki, except Balaram were killed.

The day Krishna was born it was raining heavily and there was thunder and lightning. Vasudeva came out of the jail with the child and found that the guards were in hypnotic sleep. With the help of Seshnag, the Cobra which protected the child from the torrential rains, Vasudeva managed to save the child from the cruel clutches of Kansa. Yashoda living across the Yamuna river had delivered a female child. Since she was also in a hypnotic sleep, Vasudeva exchanged the child and placed Sri Krishna near her and took away the female child. Kansa tried to get rid of the child but the child vanished into thin air by predicting that the person who was going to kill him was already born. Finally, Sri Krishna kills Kansa.

Celebration of Janmashatami
It is day of prayer and bhajans (religious songs). Holy mantras are read out. People visit the temple and offer their prayers to Sri Krishna. And pull the string of the cradle in which the image of Sri Krishna has been placed. Sweets are prepared in the houses and special dishes are cooked for the feast after the daylong fast. Plays are organized and small children dress up like Sri Krishna. The festivities are held at Gokul, which is located on the banks of river Yamuna, which is 7 miles from the city of Mathura. This is where Sri Krishna was exchanged for another child belonging to Yashoda, who is the wife of Nanda.

Ritual of Janmashtami
The festivities actually begin at midnight and reach their peak at midnight, when the birth of Sri Krishna takes place. Hymns are sung, arti is performed and conches are blown. The cradle in which the image of Sri Krishna is kept is rocked. The idol of Sri Krishna is bathed with a mixture of ghee, milk, honey oil and Gangajal known as Panchamrit... Later on the Panchamrit is distributed among the devotees along with sweets. Some fast on the first day and break it at midnight. Others fast for both the days.

People fast a day before his birthday and break the fast after his birth. They feast after the fast is broken. A clay image of Sri Krishna is made and kept in the house and worshiped. Several dishes and sweets are offered to the God and then consumed by the members of the household. A cradle is laid out and either a small child dressed up as Sri Krishna is kept in it or an idol of his. It is pulled by a string and rocked.

Janmashtami is indeed a day when adults and children offer their prayers to Lord Krishna. It is day when evil was surmounted and goodness prevailed.