One person types a lunar date once. Here’s what the whole family gets, every year.

Most calendar apps solve “remind me.” Ours solves a harder one: “remind all of us, on the right day, and help us do it properly.”

In many Vietnamese families, death anniversaries, full moon offerings and the first day of Tết follow the lunar calendar. The solar date moves every year, sometimes by weeks. The family is spread across cities and countries. And usually one person, often Mum, keeps it all in her head.

Here is what happens when she adds Grandfather’s memorial day to Nhật Nguyệt. She does it once.

The moment she saves it
She picks “14th day of the 9th lunar month” and her family group. Nhật Nguyệt converts it to this year’s solar date, and next year’s, and every year after, using a calendar engine checked against NASA new-moon data. Nobody does the math again.

30 days before
Everyone in the group gets the first reminder: on their phone, their Apple Watch or Wear OS watch, the home screen widget, or their Google Calendar if they connected it. Each person chooses up to three early reminders. The cousin abroad gets it in English, the aunt reading Chinese gets it in Chinese.

7 days before
A plan appears, built from the customs for that occasion and linked to sourced articles on why each step matters: family meeting, invite relatives, clean the altar, go to the market, the offering itself. Jobs get assigned to people, and ticked off as they’re done.

The days in between
Comments sit right inside the reminder, like a small group chat: “@Tuấn can you pick up the sticky rice?” A mention sends that person a notification, and a group admin can turn a comment into a task.

The day itself
The right prayer text opens in one tap, with the family’s names filled in, and works offline in the countryside. Photos from the day go into an album sorted by year.

Next year
It starts again automatically, with last year’s plan to copy and last year’s photos one scroll away. Over time, the reminder becomes the family’s memory of that person.

Why we built everything around this
A lunar date isn’t hard to look up. What’s hard is getting eight busy people in four places to show up for it, together. That’s the problem we’re solving: a shared memory, not a calendar entry.

It’s free for 2 family groups of 4 people, on iPhone, iPad, Android, the web, and two kinds of smartwatch.

👉 https://nhatnguyet.org/en/ung-dung