While circumstances like divorce and camp and cold weather have existed forever, the Internet gives kids a window into what other kids are doing outside their immediate environment - and if it's a good idea, they will demand they have a stake.
"These kids are part of Generation C and are thus, as we like to say, connected, creative consumers and curators," said Tina Wells, chief executive officer of Buzz Marketing Group in Haddonfield. They are part of "a much bigger community of peers - in addition to their peers in school and near home. These kids are excited to partake in the seemingly universal birthday-party experience because everyone else is."
When Jerry McTigue started halfbirthday.com in 2011, the Fairfield, Conn.-based site got eight or 10 hits a day, but these days, without advertising, it draws more than 550 page views a day, 17,000 a month. The site's growth has been steady, increasing about 20 percent a year in traffic and also in business and commissions.
That includes e-cards, e-vites, gags, and gifts for all ages. "The whole thing about the half-birthday concept is that you only have to go half out - no presents, half a cake, and half the decorations. It's not a stressful event."
That doesn't prevent people from going all out: The site links to products from other vendors, including a half-dozen gourmet dipped strawberries for $19.99.
Although half-birthday parties aren't limited to kids - for soldiers home on leave, what better time to host a get-together - the biggest advocates are adolescents who want to boast on Twitter, and mothers of six-month-olds, McTigue said. "The half birthday is a real landmark in a baby's life."
Melissa Storch of Marlton threw a party in May to celebrate son Jeffrey's half birthday, with half a cake, a ½ candle, and half-themed cups, plates, napkins, balloons, and banner.
"Having him completely changed our lives, and it's been amazing watching him grow," she said. "Why not give him a little preview of what a birthday party would be like?"
Storch kept the celebration small, just six immediate family members.
"We sang 'Happy Half Birthday,' he looked around at his whole family, and played with the toys he got," said Storch, who is considering a similar soiree when Jeffrey turns 18 months. That doesn't mean he won't also enjoy another bash when he hits the year mark. "I'm planning to have a big party with all of our friends and maybe some of the friends he makes in his music class."
Despite the growth in celebrating those special six months, half-birthday celebrations have been around a long time. For Rick Fike, 50, founder of four-year-old halfbirthdayparties.com, the celebrations were a family tradition.
"We had family members who had December birthdays and they were just run over by the holidays, so my mother, in her infinite wisdom, started throwing summer half-birthday parties," said Fike, of Phoenix. Now his business, with 2,100 Twitter followers, sells half-birthday party kits, available in basic, classic, and deluxe sizes ($14.95 to $59.95).
At Fike's own half-birthday parties, he asks guests to bring half of something, which has resulted in half a bottle of wine, a birthday card cut in half, and even a copy of the book The Joy of Sex sawed in half. The best gift wins a half prize, usually half of whatever's left over from the party.
Others getting in on the half-birthday act include Ben & Jerry's, which sends a happy half-birthday message to everyone in its database, including a buy-one-get-one ice cream coupon. (On your real birthday, your cone is free.) Pinterest offers half-themed ideas, including "We're halfing a party" invitations, half cakes, and half game ideas - kids can wear half masks to pin a tail on half a donkey.
Not everyone is a fan. Jacqueline Burt Cote, a Greenwich, Conn.-based freelance writer who blogged about the subject, sees a danger in half birthdays.
"My daughter was telling me about her friend who got a Tiffany necklace for her 11½ birthday," she recalled. "I thought that was insane. It's this culture we have where we are putting our kids up on these super-high pedestals that are setting them up for failure in real life."
Priscilla Singleton, a social worker and family therapist at the Philadelphia-based Council for Relationships, believes the merits of half-birthday parties should be judged on the spirit in which they are thrown.
"Self-esteem is built on very genuine praise and seeing accomplishments, and if there's this constant celebration with no sense of a genuineness of what they've actually done, we're heading in the wrong direction," she said. "But if it's simply another way of a family having fun, and it's a new tradition that has meaning, I'm all for it."
Singleton warns parents to avoid the message to kids that happiness comes from a collection of things - the result of any party, half or not.
"Happiness comes from relationships, positive connections, and giving back," she said.
If you can incorporate those themes, maybe by donating gifts to others, it can be a positive experience.