Anniversary Calculator

1. Choose the type: wedding, relationship, work or another event.
2. Enter the date of the event. Add a milestone year, such as 25, to count down to it.
3. Read the time since the date, the next anniversary and the countdown. Pick a "count up to" date to check a past or future day.

An anniversary calculator is a date tool that measures how long ago an event happened and when it next comes around. It turns one date into a duration and a future calendar date.

Couples use it to answer "how long have we been married?" and to plan the next celebration. Employers and employees use it for service milestones, and businesses use it for founding dates.

An anniversary is the same month and day in a later year. UK law uses the same idea for ages: under section 9 of the Family Law Reform Act 1969, a person reaches an age in years at the start of the relevant anniversary of their birth date. An anniversary count therefore works exactly like an age count, which is why the guide to anniversary and milestone dates uses the same steps.

The calculator steps forward from the event date in whole years, then whole months, then counts the remaining days. It follows the Gregorian calendar.

1. Subtract the start year from the end year.
2. Check whether this year's anniversary has come yet. When it has not, subtract 1. (An older version of this page said to add 1 when the date had passed, which gives one year too many.)
3. Count the full months since the last anniversary, then the days left over.
4. The next anniversary is the start date plus one more year. The countdown is the day difference to it.

Leap Years and Month Ends

The Calendar (New Style) Act 1750 set the Gregorian rule: every fourth year is a leap year, except century years, unless the century year is divisible by 400. So 2000 was a leap year and 2100 will not be. A February 29 date has no match in common years, and the tool shows February 28 then; some people prefer March 1. A date on the 31st moves to the last day of shorter months in the same way.

A couple married on June 14, 2014 and checks on September 30, 2026.

Calculation: 2026 - 2014 = 12, and June 14, 2026 has passed, so 12 full years. From June 14 to September 14 is 3 full months, and September 14 to 30 is 16 days. Total: 4,491 days, or 641 weeks and 4 days.

Next anniversary: the 13th falls on Monday, June 14, 2027, which is 257 days away. Their 25th, the silver anniversary in common lists, falls on June 14, 2039, 4,640 days away.

Meaning: they have been married 12 years, 3 months and 16 days, and they have about eight and a half months to plan the next celebration.

The start date, the end date and a few calendar rules decide the answer. Time zones do not, because the tool counts whole days.

Which Date You Count

Couples often celebrate a first date, an engagement or a wedding. Pick one and use it every year for a consistent count.

Leap Days

Each February 29 in the range adds a day to the total. Over 12 years that is usually 3 extra days, which is why dividing total days by 365 overstates the years near an anniversary.

February 29 and the 31st

A start on February 29 or on the 31st of a month has no exact match in some years. The tool uses the last day of the month. See what happens to February 29 birthdays for the options people use.

An Unknown Day

When only the month and year are known, enter the 1st. The years stay right, but months and days can be off by up to a month.

The same span can be written several ways. Each suits a different use.

Common Wedding Anniversary Themes

Gift lists are conventions, not rules, and different lists disagree after the first few years. The themes below appear consistently in common lists: 1st paper, 5th wood, 10th tin or aluminum, 15th crystal, 20th china, 25th silver, 30th pearl, 40th ruby, 50th gold and 60th diamond. The calculator shows a theme only for these years.

Planning a Celebration

Find the weekday of the next anniversary to book a trip or dinner. A weekend date may need an earlier booking.

Writing a Card or a Speech

Quote an exact span, such as "4,491 days", for a personal touch.

Work and Service Milestones

HR teams and staff can check when 5, 10 or 25 years of service falls. For other counts, try the date calculator.

Half-year and Odd Milestones

Read about half-birthdays and other markers in milestone dates explained.

1. Adding a Year Before the Date Arrives

Subtracting the years gives the right count only after this year's anniversary. Before it, subtract one more.

2. Dividing Days by 365

Leap days make this drift. After enough years it shows a new year a few days early.

3. Counting the Start Day Twice

The day count here is the difference between dates. A wedding yesterday is 1 day ago, not 2.

4. Forgetting the Leap-day Rule

Couples married on February 29 still have an anniversary every year. Decide on February 28 or March 1 and keep it.

5. Treating Gift Lists as Fixed

Themes differ between lists and countries. Use them as ideas, not rules.

The calendar math is exact for any Gregorian date. The only judgment calls are how to treat February 29 and month-end dates.

Subtract your wedding year from the current year, then subtract 1 more when this year's anniversary has not happened yet. Married June 14, 2014, you reach 12 years on June 14, 2026.

Enter your start date and read Total days. June 14, 2014 to September 30, 2026 is 4,491 days, leap days included.

It is the same month and day in the next year that has not passed yet. The calculator shows the date, its weekday and the days left.

You still mark an anniversary every year. The calculator uses February 28 in common years, and many couples choose March 1 instead.

It is widely called the silver anniversary. The 50th is gold and the 60th is diamond in common lists.

No. They are conventions that vary between lists and countries, so the calculator labels them as common themes only.

Yes. Choose Work or service and enter your start date to see your years of service and the next milestone.

No. It counts the days from the end date up to the anniversary, so the day before shows 1 day.

Yes. Set the "count up to" date to any day to see how long it had been and which anniversary came next.

No. Dates are processed in your browser and are not sent to us. Save keeps a result only in this browser.

• Calendar (New Style) Act 1750, section 2 (legislation.gov.uk; the Gregorian leap-year rule for century years).
• Family Law Reform Act 1969, section 9 (legislation.gov.uk; an age in years is reached at the start of the anniversary).
• ISO 8601 date and time format (International Organization for Standardization; the YYYY-MM-DD order).