About Age Differences
Couples curious about their gap, siblings settling the “you're barely older” argument, parents spacing children, genealogists mapping family trees, HR forms wanting exact differences — the age gap between two people comes up constantly, and mental math with months and leap years is unreliable past “roughly five years.”
Enter two birth dates and get the exact difference in years, months, and days, who's older, and the same gap totaled in months, weeks, and days. Half-birthday tricks and 30-day-month assumptions are exactly the errors the calendar-exact method avoids.
After one person's exact age instead of the gap? Use the Age Calculator.
How the Gap Is Calculated
Absolute difference, calendar-exact:
Gap = |older birth date − younger birth date| Years = full years between the dates Months = full months past the last year boundary Days = leftover days (borrowed from the real previous month)
Worked example: June 15, 1990 and March 20, 1995 differ by exactly 4 years, 9 months, 5 days — 57 months, 248 weeks, or 1,739 days, with the 1990 person older. Every leap day between the two dates is counted, which is where by-hand estimates usually slip.
Gaps in Months, Weeks & Days
Common round-number gaps converted (365.25-day years; your exact dates may differ by a day or two):
| Gap | Months | Weeks | Days |
|---|---|---|---|
| 1 year | 12 | 52 | 365 |
| 2 years | 24 | 104 | 731 |
| 3 years | 36 | 156 | 1,096 |
| 5 years | 60 | 260 | 1,826 |
| 7 years | 84 | 365 | 2,557 |
| 10 years | 120 | 521 | 3,653 |
A quirk worth noticing: a 7-year gap is almost exactly 365 weeks — one week of weeks per year, give or take the leap days.
Gap vs. Ratio — a Subtle Point
The gap never changes: two people born 5 years apart die 5 years apart in age. What changes is the ratio — at ages 5 and 10 one person is twice the other's age; at 45 and 50 they're practically peers. That's why gaps feel enormous in childhood and vanish in adulthood, and why “half your age plus seven,” the folk rule for socially acceptable dating gaps, is a comment on ratios, not arithmetic — a cultural rule of thumb, not anything this calculator can validate.