How far apart are two birthdays, exactly?

Enter both dates of birth to get the precise gap in years, months and days — plus the total day count, leap-year handling, and a couple of context metrics people usually ask for next.

Date of birth — Person A

Date of birth — Person B

Please enter both dates to continue.

Age gap—

—

Total days apart

—

Total months apart

—

Total weeks apart

How the gap is worked out

The tool doesn't just subtract birth years — it walks the calendar day by day between the two dates, so every leap year in between is accounted for automatically. That's why two people born exactly twelve months apart can show a gap of either 365 or 366 days, depending on whether a 29th of February falls in the interval.

The result is broken into years, months and days rather than a single decimal, because that's how people actually talk about age gaps — "6 years and 4 months" is more useful than "6.33 years," and it avoids the rounding that a decimal hides.

Reading the numbers

Relationship age gaps

For partner age gaps, a commonly cited social guideline is "half your age plus seven" as a rough floor for an age-appropriate partner. It's not a rule of any kind, just a cultural shorthand — the box above works it out automatically for the older person entered.

Sibling and family intervals

The same calculation is often used for spacing between siblings, where the exact day count matters more for birth-order and planning purposes than the rounded year figure does.

Frequently asked questions

Does it matter which date I put in first?

No. The calculator works out which of the two dates is earlier on its own and labels the older and younger person accordingly.

Why do the days and months not divide evenly?

Calendar months vary between 28 and 31 days, so the remainder after full years is expressed in whichever unit fits, rather than forced into a flat 30-day month.

Is the total day count affected by leap years?

Yes — that's the point of counting days rather than estimating them. A span that crosses more 29th-of-February dates will simply contain more days.

Can I use this for calculating age gaps between pets, or documents?

The math is generic date subtraction, so it works for any two dates — people, pets, or paperwork — as long as you enter the two dates you're comparing.

Results are calculated in your browser from the two dates you enter and follow standard Gregorian calendar rules, including leap-year correction. Provided for general informational use.