A birthday is a day or anniversary when a person celebrates his or her date of birth. Birthdays are celebrated in numerous cultures, often with a gift, party or rite of passage. Although the major religions celebrate the birth of their founders (e.g., Buddha's Birthday), Christmas – which is celebrated widely by Christians and non-Christians alike – is the most prominent example. In contrast, certain religious groups, as is the case with Jehovah's Witnesses, express opposition to the very idea of celebrating birthdays.

In most legal systems, one becomes a legal adult on a particular birthday (often between 14 and 21), and reaching age-specific milestones confers particular rights and responsibilities. At certain ages, one may become subject to military conscription or become eligible to enlist in the military, to marry without parental consent, to vote, to run for elected office, to legally purchase (or consume) alcohol and tobacco products, to purchase lottery tickets, or to obtain a driver's license.

Katheryn Elizabeth Hudson (born October 25, 1984), known by her stage name Katy Perry, is an American singer, songwriter and actress. Perry grew up with gospel music, and during her first year of high school she pursued a music career as Katy Hudson, releasing her first studio album called Katy Hudson which failed to chart. She recorded a solo album later, which was never released. After signing with Capitol Music Group in 2007, her fourth record label in seven years, she adopted the stage name Katy Perry.

She first gained recognition with the release of her first mainstream album, One of the Boys in 2008, which spawned three Billboard Hot 100 top-ten songs—"I Kissed A Girl", "Hot n Cold" and "Waking Up In Vegas". Perry supported the album with her Hello Katy Tour. In 2010, her third studio album, Teenage Dream (2010), which topped the Billboard 200 chart, and spawned five number one singles—"California Gurls", "Teenage Dream", "Firework", "E.T." and "Last Friday Night (T.G.I.F.)"—Teenage Dream was the only album (after Michael Jackson's Bad)—to do so, and the first female in history to achieve this milestone. She embarked on the California Dreams Tour, which grossed nearly $60 million worldwide. Perry re-released the album under the name of Teenage Dream: The Complete Confection on March 26, 2012, and the re-release has already spawned the number-one single "Part of Me".

Kanye Omari West ( /ˈkɑːnjeɪ/; born June 8, 1977) is an American musician, film director and fashion designer. West first rose to fame as a producer for Roc-A-Fella Records, where he eventually achieved recognition for his work on Jay-Z's album The Blueprint, as well as hit singles for musical artists including Alicia Keys, Ludacris, and Janet Jackson. His style of production originally used pitched-up vocal samples from soul songs incorporated with his own drums and instruments. However, subsequent productions saw him broadening his musical palette and expressing influences encompassing '70s R&B, baroque pop, trip hop, arena rock, folk, alternative, electronica, synthpop, and classical music.

West released his debut album The College Dropout in 2004, his second album Late Registration in 2005, his third album Graduation in 2007, his fourth album 808s & Heartbreak in 2008, and his fifth album My Beautiful Dark Twisted Fantasy in 2010. West released a collaborative album, Watch the Throne with Jay-Z in 2011, which is the duo's first collaborative album. His five solo albums, all of which have gone platinum, have received numerous awards and critical acclaim. As of 2012, West has won a total of eighteen Grammy Awards, making him one of the most awarded artists of all-time. All albums have been very commercially successful, with My Beautiful Dark Twisted Fantasy becoming his fourth consecutive No. 1 album in the U.S. upon release. West has had 5 songs exceed 3 million in digital sales as of July 2011, with "Gold Digger" selling 3,086,000, "Stronger" selling 4,402,000, "Heartless" selling 3,742,000, "E.T." selling over 4,000,000 and "Love Lockdown" selling over 3,000,000 placing him third in overall digital sales of the past decade. He has sold over 30 million digital songs in the United States making him one of the best-selling digital artists of all-time.