Six months after Lorraine C Ladish turned 59, she began to get emails – from fashion stores, the supermarket, the opticians – offering her a discount. Her half-birthday was coming up, the emails said. She used one of the offers to buy a magenta leather jacket and posted her celebration on TikTok. Ladish is a digital content creator who says she makes “a living out of sharing my age online”. But what really appealed to her about marking the midpoint between birthdays was the chance to “squeeze every second, every month, out of my late 50s”.

Ladish is not alone. Half-birthdays are having a moment. Or, at least, a fraction of a moment. On TikTok there are half-cake designs, half-birthday banners, half-birthday cards – sometimes, they are whole ones brutally sheared – and half-candles. One French brand even released a comma candle for cake decorators wishing to celebrate a half-birthday decimally.

If you dine at TGI Fridays, Ember Inns or All Bar One, you’ll likely have received half-birthday congratulations (“Here’s 25% off for your half-birthday!”, “Cocktail on us!”). In the US, Betty Crocker has half-birthday menu ideas that include serving skewered halves of hotdog buns, sandwiches cut in triangles, and colour-blocked desserts. The battenberg is the ultimate off-the-shelf half-birthday cake, or you can make your own half-cake: bake a circular cake, halve it, and stack the two pieces into a semicircular layer cake. Is all this sounding a bit half-baked?

Some people celebrate half-birthdays because their birthdays are overshadowed by other occasions. Graphic designer Cheyanne Carroll, who lives in Florida, doesn’t celebrate her own, but a few years ago she made a half-birthday card to surprise her husband, who was born on New Year’s Eve. The design – in which only the top half of the greeting appears – is now one of her top three sellers, and she posts the cards around the world. “It was just a funny thing I thought I would do for my husband. Now I see that lots of people celebrate.” Or maybe, she says, the algorithm just likes to serve her every sort of birthday, from halves to dogs. As time has gone by, she and her husband still mark his halves, but the occasion has become more low-key. Maybe your first half is always your biggest.

Other candidates for half-celebrations are children with birthdays that fall midway between winter festivities, when school is out and friends are away. It was for these children that author Erin Dealey wrote The Half Birthday Book: “Are there HALF streamers decorating HALF of the room? Small balloons HALF-filled with air? You might think you’re dreaming or still HALF asleep,” she writes. But no, “the HALF birthday buddies were there”. Dealey was born in March and doesn’t celebrate in September, but she sent a copy of the book to US television host Jimmy Kimmel, who has spoken about celebrating his, and once ambushed Snoop Dogg with half-birthday congratulations. Dealey didn’t hear back. “I’m not sure if it ever arrived,” she says.

It’s tempting to see half-birthdays as a product of the Covid pandemic and its aftermath – all those celebrations missed; all those any-excuse get-togethers once danger had passed. But back in the 2010s, my children, then in single digits, would let me know when their halves were coming – I’ve sung my share of “Happy half-birthday to you” – and then their quarters. It seemed like good maths practice at the time, but if you mark the thirds, too, you’re having more than six birthdays a year.

Instagram is full of people saying “I never thought I’d be a half-birthday-celebrating mum” – alongside videos of them succumbing with cake, or assembling “half-birthday baskets”. The ultimate half-celebration, of course, is the one that marks a person’s first six months. It’s understandable. Those six months can feel like an eternity.

On the UK-based website Gransnet, there are posters who recall celebrating their half-birthdays in the 1950s: “A small present from our mum and dad, just a bar of chocolate or sweets,” writes one. “We were given half a cake and we gave our sibling a gift,” shares another. There are literary precedents, too: Adrian Mole was 13 and three-quarters, of course. In Lewis Carroll’s Through the Looking-Glass, Humpty Dumpty recommends commemorating “unbirthdays” – 364 celebrations a year compared to just one.

Candice Meyer, a content creator from St Louis, Missouri, was careful to set the terms of her family’s tradition: no presents, just a dessert with a candle and a round of singing. “I wanted a way to slow things down and give them a moment that felt just theirs, without all the logistics that come with a full birthday,” she says. “Honestly, it feels like keeping the joy and letting go of everything else.” Half-birthdays can be wholly serious, especially when claimed as a self-care tool; the perfect occasion for a wellness retreat. “I do love the idea of it as a reset moment for anyone. A little midpoint pause to reflect and celebrate where you are,” says Meyer.

Some halves genuinely are a milestone. In Idaho, you can get a learner permit to drive at 14 and a half; it’s 15 and a half in California. At 16 and a half, you can start your application to the Australian army. Why not have cake?

Just be sure to get the day right. You may think you do, but have you factored in the length of each intervening month? If you were born on 31 August, for instance, your half-birthday might be on 1 March. Use an online half-birthday calculator to be sure.

But why bother at all? Jessica Jimenez, who runs a printables business based in Florida, with half-birthday downloads, says she likes to make the kitchen festive on half-birthdays with a banner and confetti. Her mission is: “Let’s make it not an ordinary day, you know?” She enjoys how half-birthdays are a celebration that goes under the radar. “It doesn’t pop up on your Facebook feed. It’s not in everybody’s calendar. It’s like, this is just for us and it’s fun.”

Celebrating halves might be a way to slow down time – or at least feel as if you are. Ladish stopped celebrating her halves once she entered her 60s. Now 62, she thinks she may revive them when her 70s approach. “You do not leave a decade the way you enter it,” she says. “I was not the same person at 50 as at 59. I’d lost friends. I’d had a close call with colon cancer. I went through my kids’ teenage years. Maybe when I’m 68, I will be like: ‘OK, let’s celebrate half-birthdays, because I will never be in my 60s again.’”

Ultimately, a half-birthday is a celebration of being alive. Maybe we don’t need an occasion to do that, but if it helps, why not?