Money & everyday · 3 min read
How to Calculate Age in Years, Months and Days
The method
Subtract the birth year from the current year, adjust if the birthday has not happened yet, then count remaining months and days. Counting whole months from the birth date avoids mistakes with different month lengths.
1990-05-15 → 2026-10-03
- 13,290 days in total
- About 1,898 weeks
- Next birthday in 224 days
Step-by-step working 4 steps
- 1Subtract year, month and day
2026-10-03 − 1990-05-15
- 2Count whole months, then leftover days
Add whole months to the birth date (clamping to the end of shorter months) until the next month would pass the end date; the leftover days are counted directly.
- 3Age
36 years, 4 months, 18 days
- 4Total days between the dates
13,290 days
Month-end dates
Someone born on 31 January turns “one month” old on the last day of February. The calculator clamps to the end of shorter months.
31 Jan → 1 Mar (leap year)
- 30 days in total
- About 4 weeks
- Next birthday in 336 days
Step-by-step working 4 steps
- 1Subtract year, month and day
2000-03-01 − 2000-01-31
- 2Count whole months, then leftover days
Add whole months to the birth date (clamping to the end of shorter months) until the next month would pass the end date; the leftover days are counted directly.
- 3Age
0 years, 1 months, 1 days
- 4Total days between the dates
30 days
Leap-year birthdays
On non-leap years, 29 February birthdays are usually treated as 28 Feb or 1 Mar depending on local law and convention.
29 Feb 2012 → 28 Feb 2026
- 5,113 days in total
- About 730 weeks
- Next birthday in 1 days
Step-by-step working 4 steps
- 1Subtract year, month and day
2026-02-28 − 2012-02-29
- 2Count whole months, then leftover days
Add whole months to the birth date (clamping to the end of shorter months) until the next month would pass the end date; the leftover days are counted directly.
- 3Age
14 years, 0 months, 0 days
- 4Total days between the dates
5,113 days
Total days and countdowns
Subtracting the two dates gives total days. Use the age calculator for next-birthday countdowns, and see how rates work in speed, distance and time.
Frequently asked questions
How many days old am I?
Enter your birth date in the age calculator; it reports total days.
Does the calculator store my birth date?
No. It runs in your browser and nothing is sent anywhere.
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