How to Calculate Your Exact Age in Years, Months and Days
Calculate your exact age step by step, handle month-end and 29 February birthdays, and check your age on a cut-off date for exams like UPSC and SSC.
By Awais, Founder and editor-in-chiefPublished
To calculate your exact age, subtract your date of birth from today’s date in three columns, days, months and years, borrowing from the next column whenever a number is too small. Someone born on 25 July 1998 is 28 years, 2 months and 26 days old on 21 October 2026.
Most of the time that is all there is to it. The tricky parts are month ends, 29 February birthdays and exam forms that ask for your age “as on” a fixed date. Each is covered below.
The subtraction method
Write today’s date and your birth date as day, month and year, then subtract column by column, starting with days.
Example: born 25 July 1998, age on 21 October 2026.
| Year | Month | Day | |
|---|---|---|---|
| Today | 2026 | 10 | 21 |
| Birth date | 1998 | 7 | 25 |
- Days: 21 − 25 is negative, so borrow one month. The month before October is September, which has 30 days. 21 + 30 = 51, and 51 − 25 = 26 days. October becomes month 9.
- Months: 9 − 7 = 2 months.
- Years: 2026 − 1998 = 28 years.
Age: 28 years, 2 months, 26 days.
You can check it by counting forward: 25 July 1998 + 28 years = 25 July 2026; + 2 months = 25 September 2026; + 26 days = 21 October 2026.
If the months go negative
Borrow 12 months from the years. For example, born 14 November 2000, age on 3 March 2026:
- Days: 3 − 14 is negative. Borrow February 2026 (28 days): 3 + 28 − 14 = 17 days; March becomes month 2.
- Months: 2 − 11 is negative. Borrow a year: 2 + 12 − 11 = 3 months; 2026 becomes 2025.
- Years: 2025 − 2000 = 25 years.
Age: 25 years, 3 months, 17 days.
Age in total days, weeks or months
Sometimes you need a single number, such as total days lived. Count the days between the two dates. From 25 July 1998 to 21 October 2026 is 10,315 days, which is 1,473 weeks and 4 days.
Doing this by hand means adding up whole years (365 days, or 366 in leap years) and then the remaining days, which is easy to get wrong. The age calculator gives years, months, days and totals at once, and the date calculator counts days between any two dates. Our guide on counting days between dates explains inclusive and exclusive counts.
The month-end problem
Months have different lengths, so “one month after the 31st” is ambiguous. That can make two careful methods disagree by a few days.
Example: born 31 May 2000, age on 15 March 2026.
- Borrow-the-previous-month method: days 15 − 31 is negative, so borrow February 2026 (28 days): 15 + 28 − 31 = 12. Result: 25 years, 9 months, 12 days.
- Count-forward method: 31 May 2025 + 9 months lands on “31 February 2026”, which does not exist, so it is pushed back to 28 February. From 28 February to 15 March is 15 days. Result: 25 years, 9 months, 15 days.
Both are defensible; they simply define a “month” differently. The years and whole months match, and those are what nearly every form asks for. If you need an exact day count, use total days instead.
Spreadsheets have the same issue. Microsoft documents that Excel’s DATEDIF function with the “MD” unit (days after complete months) may give a negative number, a zero or an inaccurate result, and recommends against using it. For completed years, =DATEDIF(birth_date, today, "Y") is reliable.
Birthdays on 29 February
A person born on 29 February has a real birthday only in leap years. In other years, the question is whether they turn a year older on 28 February or 1 March. The answer depends on the law where you live, and laws differ:
- Hong Kong: the Age of Majority (Related Provisions) Ordinance, section 5, treats the anniversary in a non-leap year as 1 March.
- Newfoundland and Labrador, Canada: the Age of Majority Act treats it as the last day of February.
- England and Wales: the Family Law Reform Act 1969 says a person reaches an age at the start of the relevant anniversary of their birth, without a specific rule for 29 February.
For everyday purposes it does not matter much. For legal milestones, such as the age to vote, drive or sign a contract, check the rule in your country or ask the organisation involved.
How many birthdays does a leap-day baby get?
Leap years occur every four years, except century years not divisible by 400. Microsoft’s leap year explainer gives the full rule: 1900 was not a leap year, but 2000 was. So someone born on 29 February 2008 has their next “real” birthdays in 2028 and 2032.
Age on a specific date (exam and admission cut-offs)
Many exams and schools fix the date on which your age is measured, regardless of when you apply. Always calculate your age on that date, not today.
| Rule | Age measured on | Example from the notice |
|---|---|---|
| UPSC Civil Services Exam 2026 (India) | 1 August 2026 | Age 21 to under 32: born between 2 August 1994 and 1 August 2005 (notice) |
| SSC Combined Graduate Level Exam 2026 (India) | 1 August 2026 | For the 18–27 posts: born between 2 August 1999 and 1 August 2008 (notice) |
| California kindergarten | 1 September | Child must turn five on or before 1 September (Education Code 48000) |
Upper age limits usually allow relaxations for certain categories, so read the full notice.
Worked example: “must not have attained 32”
For UPSC CSE 2026, a general candidate must not have attained the age of 32 on 1 August 2026. A candidate born on 1 August 1994 turns 32 exactly on 1 August 2026, so they have attained 32 on the cut-off date and are outside the limit. That is why the notice says candidates must be born no earlier than 2 August 1994. Someone born a day later, on 2 August 1994, is 31 years, 11 months and 30 days old on the cut-off date, and eligible.
The lesson: when a rule says “not attained” an age, your birthday falling exactly on the cut-off date counts against you. Read the birth-date range in the notice; it removes the guesswork.
Quick tips
- Write dates as day, month and year in separate columns before subtracting.
- Borrow the length of the previous month when the days go negative.
- Check your answer by counting forward from your birth date.
- For legal or exam purposes, use the exact wording of the rule and its stated cut-off date.
- When in doubt, use the age calculator, which handles leap years and month lengths automatically.
FAQ
How do I calculate my age in years, months and days?
Subtract your birth date from today’s date in day, month and year columns. When the days are negative, borrow the number of days in the previous month; when the months are negative, borrow 12 months from the years.
How old is someone born on 29 February in a non-leap year?
They still age one year every year. Whether the new age starts on 28 February or 1 March depends on local law: Hong Kong uses 1 March, while Newfoundland and Labrador uses the last day of February.
What does “age as on” mean on an exam form?
It means your age is calculated on that fixed date, not on the day you apply. Many notices also give the matching range of birth dates, which is the easiest way to check eligibility.
Why do different age calculators give different numbers of days?
Because months have different lengths, calculators can define “a month” differently near month ends. The years and complete months are the same; only the leftover days differ.