Krishna Janmashtami (Devanagari ami), also known as Krishnashtami, Saatam Aatham, Gokulashtami, Ashtami Rohini, Srikrishna Jayanti, Sree Jayanthi or sometimes merely as Janmashtami, is a Hindu festival celebrating the birth of Krishna, an Avatar of the Hindu deity Vishnu.  Krishna Janmashtami is observed on the Ashtami tithi, the eighth day of the dark half or Krishna Paksha of the month of Bhadrapada in the Hindu calendar, when the Rohini Nakshatra is ascendant. The festival always falls within mid-August to mid-September in the Gregorian calendar.
In 2010, for example, the festival was celebrated on 2nd September, while in 2011, the festival will be celebrated on 22nd August. Rasa lila, dramatic enactments of the life of Krishna, are a special feature in regions of Mathura and Vrindavan, and regions following Vaishnavism in Manipur. While the Rasa lila re-creates the flirtatious aspects of Krishna’s youthful days, the Dahi Handi celebrate God’s playful and mischievous side, where teams of young men form human pyramids to reach a high-hanging pot of butter and break it. This tradition, also known as uriadi, is a major event in Tamil Nadu on Gokulashtami.
Significance Statue of baby Krishna being carried in a basket, protected by seven hooded serpent, by Vasudeva across the Yamuna river at midnight The ritual is to fast the previous day (Saptami, seventh day), which is followed by a night-long vigil commemorating the birth of Krishna at midnight in the jail where his maternal uncle Kansa was keeping them captive, and his immediate removal by his father Vasudeva to a foster-home for safe-keeping. At midnight, the idol of the infant Krishna is bathed, adorned in new clothes and jewellery, placed in a cradle and worshiped.
The fast is completed after aarti, a special prayer. At day break, ladies draw patterns of little children’s footprints outside the house with rice-flour paste, walking towards the house. This symbolizes the entry of the infant Krishna into his foster-home i. e. their homes. In South India Celebration of Lord Krishna’s birthday as Srijayanthi in an Iyengar’s house in South India In the south, the festival is celebrated as Sri Krishnajanmashtami, Janmashtami or Gokulashtami. In Tamil Nadu, Brahmins (Iyers & Iyengars), Yadhavars, Chettiars and Pillais celebrate the festival.
Uriadi or climbing a stick containing a pot of sweet curds is also a major event in Varahur and other parts of Tamil Nadu. The pooja is performed late in the evening, timed according to the Hindu calendar to coincide with the birth of Krishna at midnight. Generally, most of the sweets and savouries are prepared on that day. Normally, a kolam (rice flour drawings on ground), also known as rangoli, drawn specially for the occasion, called ezhakoolam, decorates the front yard. Footprints representing those of Krishna are drawn from the front yard to the pooja room, representing the god entering the devotee’s home.
Karnataka and Tamil Nadu In Karnataka, Madhwas (Vaishnavas) (followers of saint Madhwacharya), Iyengars and Srivaishnavas, (followers of saint Ramanujacharya) and Smarthas (followers of Adi Shankara) make elaborate preparations for the festival. The idol of Lord Krishna is placed in a decorated mantapa. Bhakshanam (snacks and sweets in Sanskrit), that are specially prepared for the festival, are offered to Lord Krishna along with fruits and are considered to be his favourites. In some parts of Karnataka, chakli, avalakki and bellada panaka are prepared especially for the festival.
Hand made avalakki is prepared in memory of Krishna’s friend Sudhama. Legend has it that Sudhama had once offered avalakki to Krishna, as it was considered to be one of his favourite snacks. Gamaka vachana and other devotional activities are held in the evening. Divergent traditions among Srivaishnavas Within the Sri Vaishnava(Iyengar) brahmins (who are mostly found in the Tamil Nadu state, and a considerable number in Karnataka as well), there have developed slight differences as to when to observe Sri Jayanti.
There is also disagreement as to how exactly to observe the day. Should one observe upavAsa through the night, ceremonially breaking the fast the next morning, or should one eat immediately after the midnight pooja and aradhana? Broadly, there are five different opinions within the Sri Vaishnava tradition concerning this matter. The different sub-traditions are Pancaratra, Munitraya, Mannar, Tozhappar and Vaikhanasa. In a nutshell, the difference stems from lunar vs. solar month and whether to take sunrise or moonrise into consideration for determining jayanti.
Among Vadakalai Iyengars – The Pancaratra tradition is followed by Shri Ahobila Mutt, Munitraya tradition by Srirangam Srimadh Andavan Ashramam along with some other acharya purusha families, and the Mannar tradition is followed by Sri Parakala Mutt. It is named after one mannAr svAmi of unknown date who is the first extant authority arguing for this calculation. The tozhappar tradition is named after Sri Vaidika Sarvabhauma Swami, also known as Kidambi Thozhappar, who wrote a detailed text establishing the reasoning behind his tradition.  The Thenkalai iyengars adhere to the Vaikhanasa tradition.
In Maharashtra Jay Bharat Seva Sangh (Lower Parel)forming human tower to break the Dahi handi Govinda Pathaks forming human tower to break the Dahi handi Janmaashtami, popularly known in Mumbai and Pune as Dahi Handi, is celebrated with enormous zeal and enthusiasm. The handi is a clay pot filled with buttermilk that was positioned at a convenient height prior to the event. The topmost person on the human pyramid tries to break the handi by hitting it with a blunt object. When that happens the buttermilk is spilled over the entire group, symbolizing their achievement through unity.
Various handis are set up locally in several parts of the city, and groups of youngsters, called govinda, travel around in trucks trying to break as many handis as possible during the day. Many such Govinda Pathaks compete with each other, especially for the handis that dole out hefty rewards. The event, in recent times, has gathered a political flavor, and it is not uncommon for political parties, and rich community groups to offer prizes amounting to lakhs of rupees. Some of the most famous handis are at ,Dadar,Lower Parel, Worli, Mazgaon, Lalbaug, Thane and Babu Genu, Mandai in Pune. 3] Cash and gifts are offered for Govinda troops to participate; for over 4,000 handis in Mumbai, 2000 Govinda troops compete for the prizes. In Manipur Janmaashtami, popularly known in Manipur as Krishna Janma, is a significant festival celebrated at two temples in Imphal, the capital city of Manipur. The first festival is at the Govindaji temple and the second is at the International Society for Krishna Consciousness temple. Devotees of Lord Krishna gather mostly at the ISKCON temple. In North India In Uttar Pradesh where the lord was born in Mathura, his play ground Gokul and Vrindavan become more crowded and celebrations go up to a week.
In Gujarat where the city Dwarka has Dwarkadhish temple celebrates it with pomp and joy. In the eastern state of Orissa, around Puri and West Bengal in Nabadwip, people celebrate it with fasting and doing puja at midnight. Purana Pravachana from Bhagavata Purana are done from the 10th Skandha which deals with pasttimes of Lord Krishna. The next day is called Nanda Utsav or the joyous celebration of Nanda Maharaj and Yashoda Maharaani. On that day people break their fast and offer various cooked sweets during the early hour.