Krishna Janmashtami is observed as the birth anniversary of Lord Krishna. Krishna Janmashtami is also known as Gokulashtami, Shrikrishna Jayanti and just Janmashtami. In Gujarat Krishna Janmashtami is also known as Satam Atham and in South India especially in Kerala Krishna Janmashtami is observed as Ashtami Rohini.
Janmashtami is the annual celebration of the birth anniversary of Lord Krishna and it is celebrated throughout India.
Janmashtami is getting observed since the birth era of Lord Krishna. Janmashtami is the 5200+ years old ritualistic celebration of the birth anniversary of Lord Krishna. As per Vedic time chronology, in 2015 it would be the 5242th birth anniversary of Lord Krishna.
Krishna Janmashtami is significant event in most Krishna temples. The cities and towns which are related to Lord Krishna, Janmashtami is a household celebration. In the historic cities, Mathura, Vrindavan and Dwarka Krishna Janmashtami is celebrated as the birth anniversary of a family member.
The main deity which is worshipped during Janmashtami is Lord Krishna. As Janmashtami is the birth anniversary of Lord Krishna, the toddler form of Lord Krishna, which are known as Bal Gopal and Laddu Gopal, are worshipped on the day of Krishna Janmashtami.
Apart from young Lord Krishna, the biological parents of Lord Krishna i.e. Vasudeva and Devaki, the foster parents of Lord Krishna i.e. Nanda and Yashoda and the siblings of Lord Krishna i.e. Balabhadra (Lord Balarama) and Subhadra are also worshipped during Janmashtami Puja.
As per Amanta Hindu Calendar
Krishna Paksha Ashtami (23rd day) of Shravana (5th month)
As per Purnimanta Calendar
Krishna Paksha Ashtami (23rd day) of Bhadrapada (6th month)
However in both calendars Krishna Janmashtami is observed on the same day.
At most places, Janmashtami celebrations last for 2 days.
Most people in India celebrate Krishna Janmashtami based on Lunar Calendar but few temples and some regions in South India observe Krishna Janmashtami based on Solar Calendar. In most years these dates don't differ by one or two days but in some years Janmashtami date based on Lunar Calendar and Janmashtami date based on Solar Calendar might differ up to one month.
In Kerala, Tamil Nadu and in some parts of Karnataka, Krishna Janmashtami is popularly known as Ashtami Rohini and is observed based on Solar Calendar.
Krishna Janmashtami is an optional gazetted holiday in India. However, most government offices, schools and colleges keep one day off during Krishna Janmashtami.