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Anniversary Calculator Tool

Enter a date to instantly calculate how many days since. Shows all milestone anniversaries (100, 365, 1000, 10000 days) with dates and days of the week, plus monthly anniversaries, countdowns to future dates, card images and calendar export.

Last updated: 2026/10/18 Calculator Feedback & bug reports
Input

Enter a future date (such as a wedding or debut date) to see a countdown to that day.

How to count days

The start date counts as Day 1 — the usual way to count anniversaries (from Jan 1, Jan 10 is Day 10).

How to Use

1

Select Category & Date

Choose a category (dating, wedding, fan since, pet Gotcha Day and more) and enter the start date. Use the "Today" button for quick input. Japanese era input and future dates (such as a wedding date) are supported.

2

View Results

See the day count and the years/months/days breakdown instantly, plus day-based milestones (100, 1000, 10000 days), monthly anniversaries and yearly anniversaries in tabs. You can also switch how days are counted.

3

Save & Share

Copy the result as text, create an anniversary card image (PNG), add milestones to your calendar (.ics or Google Calendar), copy a share link, or save it to "My Anniversaries" on this device.

About Anniversary Calculator

A free tool to instantly calculate how many days since any date. Works for dating anniversaries, wedding anniversaries, birthdays, work start dates, the day you became a fan, and your pet's Gotcha Day. Auto-calculates milestones (100, 1000, 10000 days) and monthly anniversaries with dates and days of the week, and counts down to future dates. All processing happens in your browser - no data is sent to any server.

Features

  • Milestones & Monthly AnniversariesAuto-calculates every milestone (100, 365, 777, 1000, 10000 days), monthly anniversaries, repdigits, every 50 days, 10,000 hours and 100 million seconds, with exact dates, days of the week and achieved/remaining status.
  • Presets for Fans & Pet LoversPresets for dating, wedding, birthdays, work, fan since, debut and pet Gotcha Day. The wedding preset shows traditional anniversary names (Silver, Golden, Diamond) and the next one coming up.
  • Counting Options & CountdownsSwitch between counting the start day or the day after as Day 1 — day counts and milestone dates update together. Future dates show how many days are left.
  • Images, Calendar & Sharing in Your BrowserCard images, calendar export (.ics), share links and saved anniversaries all work in your browser. Photos are never uploaded.

Use Cases

  • Check how many days and months you've been dating
  • Turn the days since you became a fan into a card image for social media
  • Find your baby's 100-day celebration and half birthday
  • Check your wedding anniversary names and the next one coming up
  • Count down to your wedding day and add anniversaries to your calendar

FAQ

How are "days since" counted?
By default the start date counts as Day 1, which is the usual way to count anniversaries: if you started dating on January 1, January 1 is Day 1 and January 10 is Day 10. Switch to "Day after = Day 1" to count elapsed days instead (January 10 becomes Day 9); day-based milestones such as the 100th day then move one day later. Monthly and yearly anniversaries stay on the same calendar date.
When is the 100-day anniversary?
The 100th day counting the start date as Day 1. For example, if the start date is January 1, 2027, the 100th day is April 10, 2027 (April 11 if you count the day after as Day 1). This tool calculates it for you.
How is the 1000-day anniversary calculated?
Counting from the start date as day 1, the 1000th day arrives about 2 years and 9 months later. This tool shows the exact date, day of week, and Japanese era.
Are the wedding anniversary names accurate?
We show widely used traditional names: Paper (1st), Wood (5th), Tin (10th), Steel (11th) to Ivory (14th), Crystal (15th), Silver (25th), Golden (50th), Diamond (60th), Platinum (70th) and more. With the Wedding Day category, the tool also shows how many days are left until your next named anniversary. Names differ by country and source, especially for the 65th and 75th.
When is a baby's 100-day celebration?
The 100th day counting the birthday as day 1. In Japan, this is called "Okuizome" (first meal ceremony). Methods may vary by region, but this tool uses the standard calculation.
How many years is 10000 days?
10,000 days is approximately 27 years and 4 months. It is a once-in-a-lifetime milestone. Use this tool to find the exact date.
Can dates be displayed in Japanese era format?
Yes, all milestone dates show the Japanese era (Reiwa, Heisei, etc.) automatically. You can also input dates using Japanese era mode.
Can I use a future date as the start date?
Yes. Enter a future date, such as a wedding date or a debut date, to see how many days are left and the milestones counted from that day (the 100th day, the 1st anniversary and so on). For a live countdown in seconds, or days until holidays and events, try our Countdown Timer.
Are my dates or photos saved or uploaded?
Everything runs in your browser. Dates, names and the photo used for the card image are never sent to a server. Only when you use "My Anniversaries" is the data stored, in this browser on this device (localStorage). Share links keep the date after the "#" in the URL, which browsers never send to the server.
When is my monthly anniversary if we started on the 31st?
A monthly anniversary falls on the same day of the month as the start date (January 15 → February 15 is 1 month). If a month doesn't have that day, the tool uses the last day of the month: starting on January 31, the 1-month anniversary is February 28 (29 in leap years) and the 2-month anniversary is March 31. The Monthly tab lists months 1–11, 6 months, 1.5 years and more, plus how many months and days it has been today.

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