Age Calculator - Exact Age in Years, Months and Days, and Next Birthday
Enter a date of birth to see your exact age in years, months and days, how many days, weeks and hours you have lived, and when your next birthday is and which day of the week it falls on.
Maintained by Hirantha Sandaruwan Lakshan. Updated 13 October 2026.
About this tool
Change the second date to find the age on any day, such as the closing date of an application. Dates are counted as whole calendar days in your browser, and nothing is sent anywhere.
How it works
The age in years, months and days follows one rule. Starting at the date of birth, the tool adds whole months for as long as the result does not pass the chosen date, then counts the days that are left. If the birth day does not exist in a month, the last day of that month is used, so someone born on 31 January reaches one month on 28 February (29 in a leap year). The completed years are the whole years in those months.
Total days are the difference between the two dates counted on the calendar, so they do not depend on your time zone or on daylight saving. Weeks are the days divided by seven, with the remainder shown. Hours are 24 times the days, because the tool is not told the time of birth.
The next birthday is the first date on or after the chosen date that has your birth day and month, and never the day of birth itself. A birthday on the chosen date counts as 0 days to go. The tool also names the weekday of the birth date and of the next birthday.
A 29 February birthday needs a rule, and this is the tool's own: in a year that is not a leap year the birthday is counted on 28 February, the same end-of-month rule used for months. Some people and some legal systems use 1 March instead. I could not find a Sri Lankan rule for this, so ask the authority concerned if the date matters legally. A year is a leap year if it is divisible by 4, except century years that are not divisible by 400: 2000 was a leap year and 1900 was not.
Worked examples
Born 15 March 1990, age on 13 October 2026
36 years, 6 months and 28 days. That is 13,361 days, or 1,908 weeks and 5 days. The birth date was a Thursday. The next birthday is Monday 15 March 2027, 153 days away, when the age becomes 37.
Born on 29 February 2000
On 13 October 2026 the age is 26 years, 7 months and 14 days. 2027 is not a leap year, so the next birthday is counted on Sunday 28 February 2027. The next real 29 February is Tuesday 29 February 2028.
Age on a closing date
Set the second date to the closing date of an application, 31 December 2026. Someone born on 20 June 2001 is then 25 years, 6 months and 11 days old, so 25 completed years. Check the notice for how it counts age.
Frequently asked questions
How do I calculate my age in years, months and days by hand?
Subtract the birth year from the chosen year, and take one off if the birthday has not come yet that year. Then count the months from that last birthday to the chosen date, and the days after the last whole month. The tool does the same with exact rules for short months and leap years.
How do I find my age on a particular date, such as a closing date?
Type that date in the 'Age on this date' box. The result shows the completed years, months and days on that day. Read the notice to see how it wants age counted, for example on the closing date, and whether it uses completed years.
How many days old am I?
The tool shows days, weeks and hours lived. Someone born on 15 March 1990 was 13,361 days old on 13 October 2026. The hours figure is the days times 24.
When is my birthday if I was born on 29 February?
This tool counts it on 28 February in years that are not leap years, and also shows the next real 29 February. Practice differs between people and places, and some use 1 March. I could not find a Sri Lankan rule, so ask the authority concerned if it matters legally.
Why does another calculator give an age a day different?
Calculators differ on month ends (what 31 January plus one month is), on whether the last day counts, and on whether they use the time of day. This one counts whole calendar days and states its month-end rule above, so you can compare it with the other.
Does the result depend on my time zone?
No. The tool works on calendar dates, so your device's time zone and daylight saving change nothing. Only the default for 'today' uses the date in Sri Lanka (Asia/Colombo, UTC+5:30).
Is my date of birth sent anywhere?
No. The sum runs in your browser, and nothing is stored or sent.
Sources & references
Updated Oct 13, 2026