Age Calculator
Find out exactly how old you are — or how old something is — in years, months and days. Enter a date of birth and an 'as of' date, and get the exact age plus totals in days, weeks and months.
How it works
The calculator subtracts the date of birth from the reference date, breaking the result into calendar years, months and remaining days, and also expresses the total elapsed time in days, weeks and months.
Age = (As-of date) − (Date of birth)Worked examples
Born 1 January 1990, measured on 1 January 2024
An exact age of 34 years, 0 months and 0 days - the case where every part of the subtraction lands on zero.
Born 15 June 1995, measured on 10 March 2024
28 years, 8 months and 24 days. The 2024 birthday has not come round yet, so the year count stops at 28 and the months and days run from the last birthday.
A baby measured on the day it is born
A date of birth of 1 June 2026 measured on 1 June 2026 gives an age of 0 years, 0 months and 0 days, and 0 total days. Every part of the subtraction cancels, which is the correct reading for a measurement taken on the birth date itself rather than an empty result.
What this assumes, and where it does not apply
What it assumes
- Age is counted in whole calendar years, months and days between the date of birth and the date you enter - not in blocks of 365 days.
- With no measuring date given, today's date in East Africa Time (UTC+3) is used.
- Both the date of birth and the measuring date are treated as whole calendar days, so the time of day a person was born does not change the figure.
Where the result does not apply
- A 29 February birthday has no anniversary in three years out of four; the count rolls to 1 March in those years.
- Where a form or a statute defines age differently (for example age at the start of a school year), follow that rule instead.
- A pension or insurance scheme that defines age as age at the last birthday, or age nearest birthday, uses a different rule and will not match the completed years counted here.
Frequently asked questions
How is age calculated?
Age is the elapsed time between a date of birth and a reference date, broken down into years, months and days.
How many days old am I?
Enter your date of birth and today's date; the 'Total days' result tells you exactly how many days old you are.
Does this account for leap years?
Yes. The calculator uses calendar dates, so leap years are included automatically.
Why is my age one year less than I expected?
Because only completed years are counted. If your birthday falls after the measuring date in the year, the count stops at the previous birthday, exactly as it does on a form that asks for age in completed years.
Maintained by David M at Delta Tech Solutions · Figures last checked 10 October 2026 · Next check due 10 April 2027
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Add this calculator to your site with a few lines of HTML. It stays free and includes a link back to www.calculator.co.tz.
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