The film features one of the largest all-star ensemble casts in Hollywood history, starring Ashton Kutcher, Julia Roberts, Bradley Cooper, Jessica Alba, Patrick Dempsey, Alex Williams, Anne Hathaway, Jessica Biel, Jamie Foxx, Jennifer Garner, George Lopez, Hector Elizondo, Kathy Bates, Emma Roberts, Carter Jenkins, Bryce Robinson, Taylor Swift, Taylor Lautner, Eric Dane, Queen Latifah, Shirley MacLaine, and Topher Grace.

It’s Valentine’s Day in Los Angeles, florist Reed Bennett (Ashton Kutcher) proposes to his girlfriend Morley (Jessica Alba) who accepts, much to the surprise of Reed’s closest friends Alphonso (George Lopez) and Julia Fitzpatrick (Jennifer Garner). Morley changes her mind and leaves Reed later in the day. Alphonso tells Reed he and Julia knew it would never work out between him and Morley, and Reed wishes they had told him. On an airplane to Los Angeles, Kate Hazeltine (Julia Roberts), a captain in the U.S. Army on a one-day leave, befriends newly single Holden Wilson (Bradley Cooper). Kate and Holden chat, play backgammon, and tell jokes. When the plane lands, and Kate has to wait hours for the taxi, Holden offers his limousine, which Kate accepts, as she only has one day to spend with her family before she has to go back to the army.

Julia, an elementary school teacher has fallen in love with Dr. Harrison Copeland (Patrick Dempsey), but does not know that he is married to his wife Pamela (Katherine LaNasa). Reed finds out when Harrison orders flowers for his wife and girlfriend (Julia). Harrison tells her that he needs to go to San Francisco for a business trip. Wanting to surprise him and following Reed’s advice from earlier on in the day, Julia buys a plane ticket to San Francisco. Reed quickly comes to the airport and warns Julia, and she refuses to believe it and gets on the plane. She goes to the hospital where he said he would be, and inquires after him. The nurses at the counter reveal to her that he is married and tell her the name of the restaurant where he and his wife will be dining that evening. As she teaches the owner’s son, the owner allows her to dress as a waitress. Julia makes a scene at the restaurant, and gives back the toy Harrison gave her that morning. Harrison’s wife, Pamela, becomes suspicious when Julia makes a comment referring to Harrison’s ability to juggle, and Harrison is seen eating pizza alone in a condo later on that evening, implying that Pamela has left him right after Julia’s scene. One of Julia’s students, Edison (Bryce Robinson), orders flowers from Reed, to be sent to his teacher. There is a delay in the delivery of flowers, but Edison insists that Reed delivers the flowers the same day. They are for Julia; however, she suggests to Edison to give the flowers to a lonely girl in the class who also has a crush on him, which he does.

Edison’s babysitter Grace (Emma Roberts) is planning to lose her virginity with her boyfriend Alex (Carter Jenkins). The planned encounter goes awry when Grace’s mom discovers a naked Alex in Grace’s room rehearsing a song he wrote for Grace on his guitar. Meanwhile Edison’s grandparents, Edgar (Hector Elizondo) and Estelle (Shirley MacLaine) are facing the troubles of a long marriage. Grace explains to them that she wants to have sex with Alex, and says, “It’s not like I am going to sleep with one person for the rest of my life.” This upsets Estelle and leads to her telling Edgar about an affair she had with one of his business partners. The affair was while he was away, and it didn’t last long. Although she is deeply sorry for what she did, Edgar is deeply upset. Grace’s high-school friends, Willy (Taylor Lautner) and Felicia (Taylor Swift), are experiencing the freshness of new love, and have agreed to wait to have sex. On Valentine’s Day, Willy gives Felicia a large white bear that she carries around with her everywhere and Felicia gets him a gray running t-shirt (which was his) and ironed the number 13 on the back for “good luck”. They are interviewed on the news and advertise their love and support for each other.

Sean Jackson (Eric Dane), a closeted gay professional football player, is contemplating the end of his career together with his publicist Kara (Jessica Biel) and his agent Paula (Queen Latifah). Kara, a close friend of Julia’s, is organizing her annual “I Hate Valentine’s Day” party, but is becoming interested in sports reporter Kelvin Moore (Jamie Foxx) who has been sent out by his producer Susan (Kathy Bates) to cover Valentine’s Day because of a lack of sports news, and they share their mutual hatred of Valentine’s Day. Paula has hired a new receptionist named Liz (Anne Hathaway) who has started dating mailroom clerk Jason (Topher Grace). Jason is first shocked when Liz turns out to be moonlighting as a phone sex operator. Liz explains that she is only doing this because she has a $100,000 student loan to pay off, has no health insurance, and is completely broke. Jason decides that her job is too much for him to handle, but eventually comes back to the relationship after seeing Edgar forgive his wife, Estelle.

Sean comes out on national television, and Holden (who is Sean’s lover) goes back to him. Kate goes home to greet her son Edison. Willy drops Felicia off at home after a date and they kiss goodnight. Kelvin and Kara hang out at Kelvin’s news station where they later kiss, Alfonso dines with his wife, Grace and Alex agree to wait to have sex, Edgar and Estelle retell each other their marriage vows and kiss in the theater, Jason goes back to Liz and they decide to keep a bond together but to also “keep it simple”, Morley is shown walking her Border collie while trying to call Reed and the movie closes with Julia and Reed beginning a relationship.

Paper Valentines became so popular in England in the early 19th century that they were assembled in factories. Fancy Valentines were made with real lace and ribbons, with paper lace introduced in the mid-19th century. In the UK, just under half the population spend money on their Valentines and around 1.3 billion pounds is spent yearly on cards, flowers, chocolates and other gifts, with an estimated 25 million cards being sent. The reinvention of Saint Valentine’s Day in the 1840s has been traced by Leigh Eric Schmidt. As a writer in Graham’s American Monthly observed in 1849, “Saint Valentine’s Day… is becoming, nay it has become, a national holyday.” In the United States, the first mass-produced valentines of embossed paper lace were produced and sold shortly after 1847 by Esther Howland (1828–1904) of Worcester, Massachusetts.

Her father operated a large book and stationery store, but Howland took her inspiration from an English Valentine she had received from a business associate of her father. Intrigued with the idea of making similar Valentines, Howland began her business by importing paper lace and floral decorations from England. The English practice of sending Valentine’s cards was established enough to feature as a plot device in Elizabeth Gaskell‘s Mr. Harrison’s Confessions (1851): “I burst in with my explanations: ‘”The valentine I know nothing about.” ‘”It is in your handwriting,” said he coldly. Since 2001, the Greeting Card Association has been giving an annual “Esther Howland Award for a Greeting Card Visionary.”

Since the 19th century, handwritten notes have largely given way to mass-produced greeting cards. The mid-19th century Valentine’s Day trade was a harbinger of further commercialized holidays in the United States to follow.

In the second half of the 20th century, the practice of exchanging cards was extended to all manner of gifts in the United States. Such gifts typically include roses and chocolates packed in a red satin, heart-shaped box. In the 1980s, the diamond industry began to promote Valentine’s Day as an occasion for giving jewelry. The day has come to be associated with a generic platonic greeting of “Happy Valentine’s Day.” As a joke, Valentine’s Day is also referred to as “Singles Awareness Day“. In some North American elementary schools, children decorate classrooms, exchange cards, and eat sweets. The greeting cards of these students sometimes mention what they appreciate about each other.

The U.S. Greeting Card Association estimates that approximately 190 million valentines are sent each year in the US. Half of those valentines are given to family members other than husband or wife, usually to children. When you include the valentine-exchange cards made in school activities the figure goes up to 1 billion, and teachers become the people receiving the most valentines.

The rise of Internet popularity at the turn of the millennium is creating new traditions. Millions of people use, every year, digital means of creating and sending Valentine’s Day greeting messages such as e-cards, love coupons or printable greeting cards. About 15 million e-valentines will have been sent in 2010.

There are some families, however, who choose to find other means of honoring Saint Valentine on Valentine’s Day. Many of these traditions involve bonfires, for fire is said to represent passion.

Je suis desja d’amour tanné
Ma tres doulce Valentinée…

—Charles d’Orléans

At the time, the duke was being held in the Tower of London following his capture at the Battle of Agincourt, 1415.

Valentine’s Day is mentioned ruefully by Ophelia in Hamlet (1600–1601):

To-morrow is Saint Valentine’s day,
All in the morning betime,
And I a maid at your window,
To be your Valentine.
Then up he rose, and donn’d his clothes,
And dupp’d the chamber-door;
Let in the maid, that out a maid
Never departed more.

—William Shakespeare, Hamlet, Act IV, Scene 5

John Donne used the legend of the marriage of the birds as the starting point for his Epithalamion celebrating the marriage of Elizabeth, daughter of James I of England, and Frederick V, Elector Palatine on Valentine’s Day:

Hayle Bishop Valentine whose day this is
All the Ayre is thy Diocese
And all the chirping Queristers
And other birds ar thy parishioners
Thou marryest every yeare
The Lyrick Lark, and the graue whispering Doue,
The Sparrow that neglects his life for loue,
The houshold bird with the redd stomacher
Thou makst the Blackbird speede as soone,
As doth the Goldfinch, or the Halcyon
The Husband Cock lookes out and soone is spedd
And meets his wife, which brings her feather-bed.
This day more cheerfully than ever shine
This day which might inflame thy selfe old Valentine.

—John Donne, Epithalamion Vpon Frederick Count Palatine and the Lady Elizabeth marryed on St. Valentines day

 

The verse Roses are red echoes conventions traceable as far back as Edmund Spenser‘s epic The Faerie Queene (1590):

She bath’d with roses red, and violets blew,
And all the sweetest flowres, that in the forrest grew.

The modern cliché Valentine’s Day poem can be found in the collection of English nursery rhymes Gammer Gurton’s Garland (1784):

The rose is red, the violet’s blue
The honey’s sweet, and so are you
Thou are my love and I am thine
I drew thee to my Valentine
The lot was cast and then I drew
And Fortune said it shou’d be you.

For this was on seynt Volantynys day
Whan euery bryd comyth there to chese his make.

["For this was Saint Valentine's Day, when every bird cometh there to choose his mate."]

This poem was written to honor the first anniversary of the engagement of King Richard II of England to Anne of Bohemia. A treaty providing for a marriage was signed on May 2, 1381. (When they were married eight months later, they were each only 15 years old).

Readers have uncritically assumed that Chaucer was referring to February 14 as Valentine’s Day; however, mid-February is an unlikely time for birds to be mating in England. Henry Ansgar Kelly has pointed out that in the liturgical calendar, May 2 is the saints’ day for Valentine of Genoa. This St. Valentine was an early bishop of Genoa who died around AD 307.

Chaucer’s Parliament of Foules is set in a fictional context of an old tradition, but in fact there was no such tradition before Chaucer. The speculative explanation of sentimental customs, posing as historical fact, had their origins among 18th-century antiquaries, notably Alban Butler, the author of Butler’s Lives of Saints, and have been perpetuated even by respectable modern scholars. Most notably, “the idea that Valentine’s Day customs perpetuated those of the Roman Lupercalia has been accepted uncritically and repeated, in various forms, up to the present.”

The Lupercalia by name was believed in antiquity to have some connection with the Ancient Greek festival of the Arcadian Lykaia (from Ancient Greek: λύκος — lykos, “wolf”, Latin lupus) and the worship of Lycaean Pan, the Greek equivalent to Faunus, as instituted by Evander.

In Roman mythology, Lupercus is a god sometimes identified with the Roman god Faunus, who is the Roman equivalent of the Greek god Pan. Lupercus is the god of shepherds. His festival, celebrated on the anniversary of the founding of his temple on February 15, was called the Lupercalia. His priests wore goatskins. The 2nd-century Christian apologist Justin Martyr mentions an image of “the Lycaean god, whom the Greeks call Pan and the Romans Lupercus,” nude save for the girdle of goatskin, which stood in the Lupercal, the cave where Romulus and Remus were suckled by a she-wolf. There, on the Ides of February, a goat and a dog were sacrificed, and salt mealcakes prepared by the Vestal Virgins were burnt.

Since Legenda Aurea still provided no connections whatsoever with sentimental love, appropriate lore has been embroidered in modern times to portray Valentine as a priest who refused an unattested law attributed to Roman Emperor Claudius II, allegedly ordering that young men remain single. The Emperor supposedly did this to grow his army, believing that married men did not make for good soldiers. The priest Valentine, however, secretly performed marriage ceremonies for young men. When Claudius found out about this, he had Valentine arrested and thrown in jail.

There is an additional modern embellishment to The Golden Legend, provided by American Greetings to History.com, and widely repeated despite having no historical basis whatsoever. On the evening before Valentine was to be executed, he would have written the first “valentine” card himself, addressed to a young girl variously identified as his beloved, as the jailer’s daughter whom he had befriended and healed, or both. It was a note that read “From your Valentine.”