What this calculator does
An anniversary calculator answers two related questions at once: how long has it been since the date being celebrated, expressed in years, months and days, and how many days are left until the next one comes around. It works for a wedding anniversary, a work start date, or any other date worth marking each year.
The two figures are linked but not the same calculation. Years, months and days since the date is a straightforward elapsed-time count, while the next anniversary is worked out separately by finding the same month and day in the current year, or the following year if that date has already passed for this year.
The formula
Years, months and days elapsed are counted forward from the anniversary date to the reference date. The next anniversary is the same month and day as the original date, in whichever of the current or following year has not yet arrived.
| Term | Meaning |
|---|---|
| Anniversary date | The original date being counted from, such as a wedding or start date. |
| Reference date | The date the calculation is measured as of, defaulting to today. |
The inputs explained
| Field | What to enter |
|---|---|
| Anniversary date | The original anniversary date. |
| Calculate as of | The date to calculate from, normally left on today. |
When to use it
Working out how many years married or together
The years, months and days figure gives an exact answer rather than a rounded one, which is useful for anything from a card to a legal document that asks for time together to the day.
Counting down to the next anniversary
Knowing exactly how many days remain makes it easier to plan a gift, a booking or an event in time, rather than working it out from a calendar by hand.
Tracking a work anniversary
Length-of-service milestones for leave entitlements or long-service recognition follow the same maths as a personal anniversary, just measured from a start date rather than a wedding date.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the count changes as the reference date moves toward the next anniversary
A fixed anniversary date, checked as of a series of later dates.
| Checked as of | Years, months and days since | Days until next anniversary |
|---|---|---|
| today | 11 years, 1 months, 24 days | 311 |
| today+60 | 11 years, 3 months, 22 days | 251 |
| today+120 | 11 years, 5 months, 21 days | 191 |
| today+180 | 11 years, 7 months, 20 days | 131 |
| today+240 | 11 years, 9 months, 21 days | 71 |
| today+300 | 11 years, 11 months, 20 days | 11 |
Questions
How is this different from a simple days-between-dates calculator?
A days-between-dates calculator only gives the elapsed time. This anniversary calculator also works out the years, months and days breakdown and finds the next occurrence of the date, which a plain day count does not do on its own.
What if today is the anniversary itself?
The years, months and days figure shows a clean whole number of years with zero months and days, and the countdown to the next anniversary shows zero days remaining.
Can I use this for a work anniversary calculator instead of a wedding one?
Yes. Enter the start date in place of a wedding date; the years, months and days since, and the countdown to the next one, work exactly the same way.
Why does the next anniversary sometimes show next year rather than this year?
If the anniversary date has already passed for the current year by the time you check, the calculator moves straight to the following year’s date so the countdown never shows a negative number of days.
For a plain elapsed-time count between any two dates, see the days between dates calculator. To find someone’s exact age instead of time since an event, use the age calculator.