Anniversary Calculator — 100 Days, 1 Year
Dates for day 100, day 1000 and yearly anniversaries from a start date
Runs in your browser · nothing is uploaded
The day you want to count from: the day you met, married or had a baby. Defaults to today.
Defaults to today. The countdown is measured from this date.
Whether the start date counts as day 1 moves every day-count milestone by one day. Yearly anniversaries fall on the same calendar month and day, and a start on February 29 uses February 28 in common years. To compare results with someone else, use the same setting for the start date.
What it is
Counting 100 days, 200 days or ten years from a special date by flipping through a calendar is slow and easy to get wrong by a day. This anniversary calculator takes one start date and lists the day milestones from day 100 to day 3000 and the yearly anniversaries from year 1 to year 20, each with its date, weekday and countdown. Today is the default start date, so the upcoming milestones appear as soon as you open the page. Past milestones are dimmed and the next one is highlighted. Everything is calculated in your browser.
How to use
- Enter the start date: the day you met, married or had a baby.
- Check whether the start date counts as day 1. It is on by default, as is common in Korea.
- Change the reference date if needed. It defaults to today.
- Read the dates, weekdays and countdowns in the table.
- Press Make a link to copy an address that opens the same table and share it.
How it works
- Start date included (default): day N = start + (N − 1) days, so the start date is day 1.
- Start date not included: day N = start + N days, so the start date is day 0.
- Day milestones are every 100 days up to 1000, then 1500, 2000 and 3000.
- Yearly anniversaries are years 1 to 10, then 15, 20, 25, 30, 40 and 50, on the same calendar month and day.
- For any other date, use “Any day you like” to look up day N (up to 36,500) or year N (up to 100).
- A start on February 29 uses February 28 in common years.
- The countdown is the number of days from the reference date. The day itself is D-Day, past days show D+ and a number.
Examples
Start date January 1, 2024, with the start date counted as day 1.
| Milestone | Date | Weekday |
|---|---|---|
| Day 100 | 2024-04-09 | Tuesday |
| Day 200 | 2024-07-18 | Thursday |
| Day 1000 | 2026-09-26 | Saturday |
| Year 1 | 2025-01-01 | Wednesday |
Without counting the start date, every day milestone moves one day later.
Good to know
Because a day-count milestone shifts by one day depending on how the start date is counted, couples may want to agree on a method in advance. Yearly anniversaries follow the calendar, so day 365 and the first anniversary can differ, and a leap day can make day 365 fall the day before the anniversary. Use the table to plan ahead for restaurant bookings, trips or gifts by checking the date and weekday weeks in advance.
FAQ
How many days after the start is day 100?
In Korea the start date is usually counted as day 1, so day 100 is the start date plus 99 days. For a start on January 1 in a leap year that is April 9. Turn the option off to count the start date as day 0, and day 100 becomes the start plus 100 days.
How is a yearly anniversary calculated?
It is the same calendar month and day. A start on March 5, 2024 has its first anniversary on March 5, 2025. A start on February 29 uses February 28 in common years. The start-date option does not change yearly anniversaries.
Do past milestones show in the table?
Yes. Past dates are dimmed with a D+ number, and the next milestone on or after the reference date is bold with a Next tag. The reference date defaults to today and can be changed.
How do we make sure we get the same dates?
Use the same start date and the same start-date option and the tables will match. The Make a link button builds an address that carries both, so you can send it as is.
Does the share link send my date to a server?
No. The start date and option live after the # in the address, which the browser reads locally and never sends to a server.
