How it works
The calculator uses real calendar dates, so leap years and months of different lengths are handled automatically — a total-days count is not simply years × 365. The next anniversary is the same month and day in the next year that has not yet passed (or today, if today is the anniversary).
Frequently asked questions
What counts as the start date?
Whatever you and your partner count — first date, or the day you became a couple. The math only needs a date.
Can I check a past date?
This version counts to today. For a past milestone, use the date-duration style count between the two dates.