You've been alive for thousands of days — and someone you love is about to hit a perfectly round number of them. That's a k-day: a milestone birthday that only comes around every 2.7 years. Happy K-Day finds the next one in your life and makes sure there's cake.
Free · No accounts · Nothing leaves your phone · In 40 languages
Not years — days. Enter your birthday and meet the number nobody ever told you about.
Every multiple of 1,000 days is a k-day. Here's when they happen — chances are someone in your family is closer to one than you think.
| k-day | age it arrives | what that number feels like |
|---|---|---|
| 1,000 days | 2 years, 9 months | the first big number |
| 5,000 days | 13½ years | old enough to want a real party |
| 10,000 days | 27 years, 4 months | everyone's first five-digit day |
| 15,000 days | 41 years | right between the "round" birthdays |
| 20,000 days | 54¾ years | a lifetime of memories in the making |
| 25,000 days | 68½ years | when every day starts to feel more valuable |
| 30,000 days | 82 years | a number very few people get to count |
A k-day lands on an ordinary Tuesday nobody saw coming. That's exactly what makes it unforgettable.
"My mother has had 68 birthdays, and honestly, they'd started blurring together. Then the app told me she was 43 days away from 25,000 days alive. We put 25 candles on the cake — one per thousand. She cried. Then she asked who's next, and now she tracks all of us."
"Turning 27 felt like nothing. But 10,000 days on Earth? That's a number with weight. We did a rooftop party with a countdown at midnight, like New Year's Eve but for one person. My friends checked their own dates before the night was over — that's the trap, and it's a lovely trap."
"My granddaughter found out I was about to reach 30,000 days. Thirty thousand! I was there for all of them and had never counted one. They came with the great-grandchildren, and every guest got a card with the day number when they first met me. I know my next number. I intend to make it."
Three screens, no manual needed. Add birthdays from your contacts, by hand, or by simply asking someone — the app does the counting and the reminding.
A heads-up before every k-day — you pick how many days ahead, at what hour, or never. Your call.
When someone's k-day arrives, the whole app celebrates. Share a milestone card in one tap.
The next k-day lives on your home screen and updates itself daily.
From Icelandic to Thai — 40 languages, from day one.
No account, no ads, no analytics. The app makes zero network requests — your contacts never leave your phone.
A designed "party at night" palette, not an automatic inversion.
Launching on the App Store — free, in 40 languages. The App Store link will appear right here on launch day.
Questions? Talk to usUntil then: check the calculator and find out whose k-day you'd already be planning.
🤖 Android is on the way. The app is finished and in testing — it lands in the Play Store as soon as Google gives the green light.
Happy K-Day