Wedding Anniversary Calculator
Use this wedding anniversary calculator to see how long you have been married, the next anniversary date and countdown, monthly and six-month milestones, and any target anniversary year.
Written and checked by TheToolNet Editorial Team · Last reviewed: August 22, 2026 · How we check date tools
Calendar years and months are not fixed day counts. The tool handles varying month lengths and lets you choose a February 29 convention.
Calculate your wedding anniversary
Enter the wedding date; the as-of date defaults to today. The same calendar logic also works for relationships, founding dates and other events.
Calculate a wedding anniversary
Enter the wedding date and an as-of date. The result counts completed calendar years first, then calendar months, then remaining days. It also gives the next wedding anniversary number, date and days remaining.
For a wedding on April 20, 2016, the 10th anniversary is April 20, 2026. The anniversary number changes on the calendar anniversary, not after an average 365.25-day interval.
Monthly anniversary calculator
A monthly anniversary adds whole calendar months to the event date. When the target month is shorter, this calculator uses its last valid day. Therefore one month after January 31, 2026 is February 28, 2026; two months after the original event is March 31, 2026.
A six-month anniversary uses the same rule but advances in six-calendar-month intervals. Six months after August 31 is the last valid day of February.
Anniversary calculator in years
To calculate a numbered anniversary, add that number of calendar years to the original month and day. The tool supports target anniversaries from 1 through 500 years and separately shows the next upcoming yearly milestone.
| Wedding date | Target | Anniversary date |
|---|---|---|
| 2016-04-20 | 10 years | 2026-04-20 |
| 2000-12-15 | 25 years | 2025-12-15 |
| 2024-02-29 | 1 year | 2025-02-28 or 2025-03-01, by chosen convention |
February 29 anniversary rule
A February 29 date has no exact month-and-day match in a non-leap year. Different legal, social and software contexts may use February 28 or March 1. The calculator does not hide that choice: select the convention you need before calculating.
Worked anniversary examples
Six-month anniversary
Start on March 10, 2026. Adding six calendar months gives September 10, 2026.
Anniversary year calculation
From September 10, 2018 through September 9, 2024, only five full anniversaries have occurred. The sixth occurs the next day.
Event on the 31st
For monthly milestones from January 31, calculate each milestone from the original date. February uses its last day, while March returns to March 31 rather than drifting to March 28.
Scope and limitations
This tool calculates Gregorian calendar dates from year 100 through 9999 as supported by the input control. It does not apply jurisdiction-specific legal anniversary rules, religious calendars, business-day adjustments, or time-of-day differences. Total days are counted between midnight UTC representations of the calendar dates to avoid daylight-saving distortions.
Frequently asked questions
How do I calculate an anniversary date?
Add the anniversary number in calendar years to the original event date, using an explicit February 29 rule when necessary.
How do I calculate a monthly anniversary?
Add whole calendar months to the event date. If the target month does not contain the original day, use the month’s last valid day.
When is a six-month anniversary?
It is six calendar months after the original event date, with a last-valid-day adjustment for a shorter target month.
Can this be used as a wedding anniversary calculator?
Yes. It reports elapsed time, the next wedding anniversary and countdown, and a selected target anniversary date.
Related date and time tool
Working with machine-readable times instead of calendar milestones? Use the Unix timestamp conversion tool.