The fifth or the last day of Diwali is Bhaiya Dooj, popularly know as Bhai Dooj. The reason why this festival is known as bhai dooj is that it falls on the second day after the new moon (Amavasya) that is the Dooj day. And it is a day to pray for the long life of the brother, who is referred as “bhayya or bhai”. According to religious scriptures, Yamaraj, the God of death, went to visit his sister's house after a long period of separation. His sister, Yami was very happy to see him and welcomed him by putting an auspicious mark on his forehead for his welfare. Yami and Yamraj then shared a meal. He was so pleased with his sister's reception, he proclaimed that every year, on the dooj day, if a sister puts a tilak on her brother's forehead, then no one can harm her brother. Till date, this tradition is followed. Sisters perform puja for their brothers’ safety and well being. Brothers in return give gifts to their sisters as a token of love.

As the legend goes Yamraj, the God of Death visited his sister Yamuna on this particular day. That is why this day of Bhayyaduj is also known by the name of "Yama-Dwitiya" or Bhathru Dwithiya. Bhatri Ditya is a special occasion amongst brothers and sisters and is observed as a symbol of their mutual love and affection.

Some other legend says that Bhagawaan Mahavir found nirvana on this day.
The festival of Diwali is incomplete without bhai dooj. It is referred as “Bhaiyya-Duj” in the Hindi-speaking belt, “Bhav-Bij or Bhaubeej” in the Marathi-speaking areas, “Bhai Fota” in Bengal and "Bhai-Tika" in Nepal. The essence of the Bhai dooj festival is that it is celebrated to strengthen the love between brothers and sisters.

Regional Variations
The tradition of celebrating Diwali in North India is based on the return of Lord Ram from exile to Ayodhya. But in South India the tradition is of Krishna defeating demon Naraka with the help of Satyabhama. It is a common custom in the South that during the First Deepavali following the marriage, the newly weds go to the bride's parental home for revelry.  In the East it is celebrated as Kali Chaudas as the day allotted to the worship of Maha-Kali or Shakti. Deepavaali is also considered as a harvest festival in some parts of the country.

There are numerous legends and local customs associated with this festival, but common to all is the lighting of homes, pathways, temples, and even public buildings, with hundreds of small clay lamps and candles. Firecrackers, thought to frighten away evil spirits are also used with abandon, which makes this a popular merry-making festival for children. 

Chopda Pujan: Diwali also represents the start of a new business year so all businesses close their accounts and present them to Lakshmi and Ganesh during the Chopda Pujan.
Muharat Pujan: All business establishments and families perform muharat pujan or veneration of their books.

On Diwali day, business establishments remain open, corporate sector distributes Diwali gifts lavishly. Sweets and Dry fruits, Silver coins and other household items are popular give-aways. Among the special eatables for this occasion Murukku in the South and Chakli in Maharashtra occupy a unique place. Greeting Cards, Rangoli and New Clothes vie with each other to catch the people’s fancy and purse.

Newspapers and Magazines are not left far behind in commanding people’s attention. The endless supplements to the dailies and attractive Diwali Special Issues of all types of Magazines in all languages need no special mention. These Magazines are Collectors’ items and contain attractive pictures and jokes particularly about the newly weds. In some places Exhibitions of such Special Issues are held which is really a sight to be experienced.

Philosophical Significance
So, the sum and substance of the message connected with Deepavali is that it is a five-day festival, beginning with Dhanteras and ending with Bhai Dooj. Some of the human values we can learn from these traditions are as follows.

The Narakasura Vadh by Sathyabhama could mean that parents should not hesitate to punish their children when they step in to the wrong path.  Its message is that the good of the society should always prevail over one's own personal bonds and affiliation. Padwa is symbolic of love and devotion between the wife and husband. On this day newly-married daughters with their husbands are invited for special meals and given presents. Bhai dooj is a symbol for the love and affection between brothers and sisters.

Deepavali is also an occasion for spiritual exhilaration, lighting up of all darkness, socially as well as personally, outwardly and inwardly, for the purpose of allowing an entry of the Supreme Light of God into the hearts of all people.

Dipavali means 'the line of lights'. 'Dipa' is light; and 'Avali' means line. So, Dipavali or the festival of the line of lights is the celebration of the rise of Knowledge. It is also the celebration of the victory of the Sattvic or divine elements in us over the Rajasic and Tamasic or baser elements which are the real Asuras, the Rakshasas, Narakasura and others.

The whole world is within us. The macrocosm can be identified with our own microcosm. The whole cosmos can be found in a microscopic form in our own body. Rama-Ravana-Yuddha, Narakasura-Vadha, or the Battle of Kurukshetra and all such Epic wars – everything is going on inside us. The festival of Deepavali is thus a chance, an opportunity for every one of us to contemplate in our own selves the holy possibility of self-mastery, self-subjugation, self-effacement, self-obliteration and self-abnegation by fully wiping out the self-centered egoistic tendencies in us leading to the rise of daivi-sampatthi by controlling asuri-sampatthi. This is considered as lustre or radiance emanating from Self-Knowledge.

Bhagavati Mahalakshmi, the Goddess of prosperity, does not merely mean the Goddess of wealth in a material sense. Lakshmi does not mean only gold and silver. Lakshmi means prosperity in general, positive growth in the right direction, a rise into the higher stages of evolution. This is the advent of Lakshmi. Progress and prosperity are Lakshmi.

In the Vishnu Purana we are told if Narayana is like the sun, Lakshmi is like the radiance of the sun. They are inseparable. Wherever Narayana is, there is Lakshmi. Wherever is divinity, there is prosperity.

Bhagavad Gita concludes
yatra yogeswarah krishno yatra paartho dhanurdharah
tatra shreervijayo bhootirdhruvaa neetirmatirmama // 18.78 //
Wherever there is Krishna, The Lord of Yoga and wherever there is Partha, the Archer, I think, there will surely be prosperity, victory, welfare and morality.

So on this day of Deepavali let us all worship the Supreme God who is the source of all conceivable virtues, goodness and prosperity, which is symbolized in illumination, lighting and prayer on this auspicious event. In short, this is a day of rejoicing for the victory of the Good over Evil, Light over the Darkness, Wisdom over Ignorance, Equality over Discrimination and Freedom over Bondage.

Aum tamasoma jyotirgamaya| sarve janaa sukhino bhavantu|