Anniversary Day Counter
＋More features: anniversary list and every-100-day milestones
The anniversary and the reference date are taken from the form above.
Dates of the 1st to 10th anniversaries
Every-100-day milestones (day 100 to day 1,000)
The first day counts as day 1 (the same counting used for Japan's 100th-day baby celebration, okuizome).
Just enter a birthday or an anniversary — such as the day you started dating — and instantly see what day number today is, plus milestone dates like day 1,000 and day 10,000. Great for planning a baby's 100th-day celebration or checking a couple's milestones.
How to use
- Pick the anniversary (a birthday, the day you started dating, your favorite idol's debut day, and so on).
- The moment you pick it, you see what day number today is, along with each milestone's date, weekday and days to go. No button needed.
- Add future milestones to your calendar and use them to plan a celebration.
How it is calculated
- Days are counted on the Gregorian calendar, the current calendar (leap years handled).
- Date of day N = anniversary + (N−1) days (the anniversary itself is day 1)
- Milestones shown: days 100, 200, 300, 365, 500, 777, 1,000, 2,000, 3,000, 5,000, 7,777, 10,000, 15,000, 20,000, 25,000 and 30,000.
- Example: someone born on July 18, 1990 reaches day 13,150 on July 18, 2026. Day 20,000 of their life is April 19, 2045.
Sources and assumptions
- Arithmetic based on the calendar system (Gregorian calendar).
Assumptions and notes
- Year-based anniversaries (such as a first anniversary) fall on the same month and day, which can differ from day 365/366 counted in days.
Frequently asked questions
Does “100 days together” include the day we started dating?
There are two ways to count, and this tool counts the anniversary itself as day 1 (day 100 = 99 days later). Agreeing on the counting method with your partner avoids mix-ups.
How old is someone on their 10,000th day?
About 27.4 years old (10,000 ÷ 365.25 ≈ 27.4 years). Day 20,000 comes at about age 54.8 and day 30,000 at about age 82.1. Celebrating these as major life milestones is becoming popular.
Can I use it for anniversaries still to come, such as a wedding anniversary?
Yes. For past dates it shows what day number it is; for future milestones it shows how many days are left — handy for planning long-term anniversaries such as a silver wedding.