Birthday is the name given to the date of the anniversary of the day of a person's birth. People in many cultures celebrate this anniversary. In some languages, the word for birthday literally translates as "anniversary". Birthdays are traditionally marked by celebrations including a birthday party or, in some particular cases, a rite of transition. In Judaism, the perspective on birthday celebrations is disputed by various rabbis. In the Hebrew Bible, the one single mention of a celebration being held in commemoration of someone's day of birth is for the Egyptian Pharaoh, while Leviticus 18:1-3 states "And the LORD spoke to Moses, saying, "Speak to the people of Israel and say to them, I am the LORD your God. You shall not do as they do in the land of Egypt, where you lived".

The bar mitzvah of 13-year-old Jewish boys, or bat mitzvah for 12-year-old Jewish girls, is perhaps the only Jewish celebration undertaken in what is often perceived to be in conjunction with a birthday. However, the essence of a bar/bat mitzvah celebration is entirely religious in origin (i.e. the attainment of religious maturity according to Jewish law) and not secular, despite modern celebrations where the secular "birthday" element often overshadows the essence of it as a religious rite. With or without the "birthday" celebration, the child nevertheless becomes a bar or bat mitzvah, and the celebration can be on that day or any date after it.

Since the foundation of Christianity historically lies in Judaism, if there is a stance against the celebration of birthdays, it often mirrors the Jewish religious arguments. Few branches of Christianity, however, actually hold any official stance in regards to birthdays, be it in favour or against. Orthodox Christianity prefers the celebration of name days only, though it is not because of any active theologically-based prohibition or discouragement. Some Christian communities, especially in the Hispanosphere, celebrate both naming days and birthdays. It is Jehovah's Witnesses that do not celebrate birthdays at all, actively discouraging or prohibiting it. They point to the birthday celebrations in the Bible for Pharaoh and for Herod, the latter being the occasion for the beheading of John the Baptist.

In the branches of Christianity where there is active discouragement or prohibition against birthdays, by default, this also affects their stance in regards to Christmas. After all, in its religiously-presented form, Christmas is the conmemoration of the birth of Jesus of Nazareth, that is, a birthday celebration for Jesus. Hence, Jehovah's Witnesses do not espouse the celebration of Christmas either, although additional theological arguments are also cited. Because of the very existence of Christmas as an integral celebration espoused by most branches of modern Christianity, it could be argued that this constitutes implicit acceptance of birthdays, contrary to this, it might put into question the legitimacy of Christmas altogether.

In Islam, some Sunni and Shia Muslim scholars oppose birthdays. This stance stems from the Hadith which forbids the adoption of festivities and occasions of other religions or paganism into Islam.

The birthday cake is traditionally highly decorated, and typically covered with lit candles when presented, the number of candles signifying the age of the celebrant. The person whose birthday it is may make a silent wish and then blow out the candles. After that, the person can open their presents. It is also common for the person celebrating their birthday to cut the initial piece of the cake as a newlywed couple might with a wedding cake.

Birthday cakes date back as far as the Middle Ages when the English would conceal symbolic items such as gold coins, rings and thimbles inside their cakes. Each item was associated with a prediction. For example, a person finding a gold coin in a birthday cake would supposedly become wealthy; a person discovering a thimble would never marry. Sometimes special candles are substituted for the many individual candles in the shape of a numeral. For example, on the first birthday, there may be one candle on the cake in the shape of the numeral one, and on the tenth birthday there may be two candles on the cake, one in the shape of the numeral one followed by the other in the shape of the number zero.

In addition to parties, it is common for people to receive gifts on their birthdays or surprise parties. However, sometimes it is expected of the person celebrating their birthday to treat their party guests instead; this varies depending on the local culture and may involve party gifts or other gestures.

In most English-speaking countries it is traditional to sing the song Happy Birthday to You to the honored person celebrating a birthday. Happy Birthday songs are common worldwide. Similar songs exist in other languages such as "Zhu ni sheng ri kuai le" in Mandarin Chinese, "Lang zal hij/zij leven" in Dutch, "Õnne soovime Sul" in Estonian, "Zum Geburtstag Viel Glück" in German, "Nα ζήσεις και χρόνια πολλά " in Greek, "Que los cumplas feliz" or "Feliz cumpleaños a ti" in Spanish, "Parabéns a você" in Portuguese, "Maligayang Bati" in Filipino, "Sto lat" in Polish, "Lá Breithe Shona Duit" in Irish, "Ja må du leva" or "Med en enkel tulipan" in Swedish, "Joyeux Anniversaire" or "Bonne Fête" in French, "Tanti Auguri a te" in Italian and "Iyi ki dogdun, Mutlu Yillar Sana" in Turkish.[citation needed] This song is a common greeting used on birthdays, along with greeting cards and verbal greetings with messages such as "I wish you a Happy Birthday" or "Happy Birthday." In Denmark, aside from cards and songs, the Danish flag is often raised and used as decorations at birthday parties.

* In most legal systems, one becomes a legal adult on a particular birthday (often 18th or 21st), and at different ages gains different rights and responsibilities — voting, certain drug use (for example, alcohol, purchasing tobacco), eligibility for military conscription or voluntary enlistment, purchasing lottery tickets, vehicle driving licences, etc.[citation needed]
* Many cultures have one or more coming of age birthdays:
o Jewish boys have a bar mitzvah on or around their 13th birthday. Jewish girls observe a bat mitzvah on or around their 12th birthday, or sometimes on or around their 13th birthday in Reform and Conservative Judaism.
o In some Christian traditions, generally Catholic and Anglican, Confirmation is the ritual by which a young person receives a Sacrament thought to bestow certain gifts of the Holy Spirit. The timing of the reception of this Sacrament serves, on a sociological level, as a sort of "rite of passage" into adulthood.
o In Hispanic countries the quinceañera celebration traditionally marks a girl's 15th birthday.
o Some girls and a few boys in the United States have "sweet sixteen" birthday parties.
o In the United Kingdom 18th and 21st are traditional coming of age birthdays.[citation needed]
o In some Asian countries, the 14th birthday is celebrated as the day one becomes a man, or a woman, in society.[citation needed]
o Many Filipino girls celebrate their 18th birthdays with a cotillion and debutante ball, commonly known as a debut.[citation needed]
o In India, the 12th or 13th birthday is replaced with a grand "thread ceremony." The child takes a blessed thread and wears it, symbolizing his coming of age. This ceremony is more common amongst boys in the Hindu culture.
* The birthdays of historically significant people, like national heroes or founders, are often commemorated by an official holiday. Some saints are remembered by a liturgical feast (sometimes on a presumed birthday). By analogy, the Latin term Dies natalis is applied to the anniversary of an institution (such as a university).
* A person's Golden or Grand Birthday, more commonly referred to as the "Star Birthday" occurs when they turn the age of their birth day (i.e. when someone born on the 12th of the month turns 12).

Some notables, particularly monarchs, have an official birthday on a fixed day of the year, which may not necessarily match their actual birthday, but on which celebrations are held. Examples are:

* Jesus of Nazareth's traditional birthday is celebrated as Christmas Day around the world: 25 December. As some Eastern churches use the Julian calendar, 25 December falls on 7 January in the Gregorian calendar every year until 2100.
* The King's or Queen's Official Birthday in Australia, Fiji, New Zealand, and the United Kingdom; in Canada this day is known as Victoria Day.
* The Grand Duke's Official Birthday in Luxembourg: 23 June.
* The King's official birthday in Belgium: November 15 (on saint Leopold, liturgical feast of the dynasty's founder's patron saint).[citation needed]
* Koningsdag or Koninginnedag in the Kingdom of the Netherlands is fixed on 30 April (Queen's Day; celebration of the reigning Queen's accession). Queen Beatrix fixed it at the birthday of her mother, the previous Queen, to avoid the winter weather associated with her own birthday in January.
* The 21st of August is the date on which the Irish celebrate the birthday of Aoife Cooper, the Druid Queen who was driven mad by secret love (Paramore).

While it is uncommon to have an official holiday for a republican head of state's birthday, this can become a permanent posthumous honour, for example George Washington's and Abraham Lincoln's birthdays are celebrated together as Presidents' Day.

In some Roman Catholic and Eastern Orthodox countries such as France, Bulgaria, Hungary, or Greece, it is common to have a 'name day'/'Saint's day'. This is celebrated in much the same way as a birthday, but is held on the official day of a saint with the same Christian name as the birthday person; the difference being that one may look up a person's name day in a calendar, or easily remember common name days (for example, John or Mary); however in pious traditions, the two were often made to concur by giving a newborn the name of a saint celebrated on its birthday, or even the name of a feast, for example, Noel or Pascal (French for Christmas and "of Easter").


People born on February 29, which occurs only during leap years, often celebrate their birthday in other years on February 28, or March 1 (the first day they have, measured in whole years, a new age).

In school, a half-birthday or other unbirthday is sometimes celebrated for those whose birthdays do not fall on a school day (especially for birthdays falling during holiday and vacation periods).

A person's birthday is usually recorded according to the time zone of the place of birth. Thus people born in Samoa at 11:30 pm will record their birthdate as one day before Coordinated Universal Time (UTC) and those born in the Line Islands will record their birthdate one day after UTC. They will apparently be born two days apart, while some of the apparently older ones may be younger in hours. Those who live in different time zones from their birth often exclusively celebrate their birthdays at the local time zone. In addition, the intervention of Daylight Saving Time can result in a case where a baby born second being recorded as having been born up to an hour before their predecessor.

Birthday Quotes:

* "Our birthdays are feathers in the broad wing of time." -- Jean Paul Richter
* "The more things change, the more they remain the same." -- Alphonse Karr
* "Every ten years a man should give himself a good kick in the pants." -- Edward Steichen
* "A diplomat is a man who always remembers a woman's birthday but never remembers her age." -- Robert Frost
* "Birthdays are good for you. Statistics show that the people who have the most live the longest." -- Larry Lorenzoni
* "A well adjusted woman is one who not only knows what she wants for her birthday, but even knows what she's going to exchange it for." -- Anonymous
* "There is still no cure for the common birthday." -- John Glenn
* "Because time itself is like a spiral, something special happens on your birthday each year: The same energy that God invested in you at birth is present once again." -- Menachem Mendel Schneerson
* "We know we're getting old when the only thing we want for our birthday is not to be reminded of it." -- Anonymous
* "A birthday is just the first day of another 365-day journey around the sun. Enjoy the trip." -- Anonymous
* "I never forget my wife's birthday. It's usually the day after she reminds me about it."
* "When I have a birthday I take the day off. But when my wife has a birthday, she takes a year or two off."
* "I have nothing to give as a gift but I promise to always remember your birthday." -- Victor Ukegbu Ogbonnaya
* "Birthdays are just nature's way of telling us to eat more cake." - - Anonymous
* "Think of birthdays this way: you're not getting older, you're getting wiser."-- Anonymous
* "You have no birthday because you have always lived; you were never born, and never will die. You are not the child of the people you call mother and father, but their fellow-adventurer on a bright journey to understand the things that are." -- Richard Bach
* "Fly free and happy beyond birthdays and across forever, and we'll meet now and then when we wish, in the midst of the one celebration that never can end." -- Richard Bach

In probability theory, the birthday problem, or birthday paradox pertains to the probability that in a set of randomly chosen people some pair of them will have the same birthday. In a group of at least 23 randomly chosen people, there is more than 50% probability that some pair of them will both have been born on the same day. For 57 or more people, the probability is more than 99%, and it reaches 100% when the number of people reaches 366 (by the pigeon hole principle, ignoring leap years). The mathematics behind this problem leads to a well-known cryptographic attack called the birthday attack.


The birthday problem asks whether any of the 23 people have a matching birthday with any of the others — not one in particular. (See "Same birthday as you" below for an analysis of this much less surprising alternative problem.)

In a list of 23 people, comparing the birthday of the first person on the list to the others allows 22 chances for a matching birthday, but comparing every person to all of the others allows 253 distinct chances: in a group of 23 people there are 23×22/2 = 253 pairs. The approximate probability that two people chosen from the entire population at random have the same birthday is 1/365 (ignoring Leap Day, February 29), and presuming all birthdays are equally probable.[2] Although the pairings in a group of 23 people are not statistically equivalent to 253 pairs chosen independently, the birthday paradox becomes less surprising if a group is thought of in terms of the number of possible pairs, rather than the number of individuals.