How the calculation works
The calculator works with whole calendar days. For an age it counts the whole years first, then the whole months, and the days that are left over.
Days between = end date − start date, in whole days
Age = whole years, then whole months, then remaining days since the last monthly anniversary
A birthday on a day that does not exist in a month (such as the 31st) moves to the last day of that month when counting months.Worked example
Age: born 15 May 1990, on 12 November 2026.
- From 15 May 1990 to 15 May 2026 is 36 whole years.
- From 15 May 2026 to 15 October 2026 is 5 whole months.
- From 15 October to 12 November is 28 days.
- Result: 36 years, 5 months and 28 days. The next birthday is 15 May 2027.
What this calculator does not include
- Time of day and time zones. Only dates count.
- Working days, weekends and holidays.
- Dates before the year 1000 and calendars other than the Gregorian one.
Amounts are rounded for display only; the calculation itself is not rounded. Results are estimates for information, not financial advice. Last updated: 12 November 2026.
Frequently asked questions
How is my exact age calculated?
The calculator counts whole years from your birthday, then whole months, then the remaining days. Born on 15 May 1990, on 12 November 2026 you are 36 years, 5 months and 28 days old.
What if I was born on 29 February?
The calculator treats 1 March as your birthday in years that are not leap years, so the countdown to your next birthday always lands on a real date.
Is the end date included in the number of days between two dates?
No. The days between 1 January and 2 January is 1. If you want to count both the first and the last day, add 1 to the result.
Does daylight saving time change the result?
No. The calculator counts calendar days, not hours, so clock changes never shift the answer.
Can I calculate my age on a date in the past or future?
Yes. Fill in the "Age on" date. Leave it empty to use today’s date. The date of birth must come before it.