Krishna Janmashtami is the birth celebrations of the Lord Krishna - also known as the eighth Avatar of Lord Vishnu.
The birth celebrations are celebrated on the Ashtami of Krishna Paksha of Bhadrapada - (August-September).
Krishna Jamashtami is a day of fasting, mirth and joy. It is also celebrated by the breaking of dahi handi in the western parts of India.
Major celebrations are in Mathura, Vrindavan and Gokul all of which fall in U.P.
The festival is generally celebrated by fasting through the day and heralding the arrival of the Lord Krishna at midnight. Images of Lord Krishna are placed in Swings, Jhankis in temples and in homes. The day is spent in singing the praises of Lord Krishna and decorating his Jhankis.....All in all a day of fun, joy and happiness...
Personally a day of double celebration for me as it happen's to be my father's birthday too....Cheers!