What this calculator does
Find out exactly how old someone is in years, months and days, on today's date or any other. Your age in whole years is easy to say. An exact age takes careful counting, because months have different lengths and leap years add a day. This calculator does that counting for you.
Enter a date of birth and the date you want the age on. Along with the exact age, you get the totals in months, weeks, days and hours. You also see the weekday you were born on, and the date of your next birthday with a countdown.
Where it's used
Why this math matters outside the classroom:
- Exact age. Someone born on March 15, 2000 is 26 years, 7 months and 4 days old on October 19, 2026.
- Eligibility dates. Families check whether a child will have reached a required age by a school or sports cutoff date.
- Age in days. People count the total days they have been alive to mark a milestone such as their 10,000th day.
- Forms and records. Clerks confirm an age from a date of birth when filling in an application.
How to use it
- Enter the date of birth.
- Leave the second date as today, or change it to find the age on a past or future date.
- Read the exact age and the totals underneath. The next-birthday line shows the date, its weekday and the age you'll turn. It counts from the second date you entered, which isn't always today.
What the inputs mean
- Date of birth
- The calendar date of birth. The time of day you were born isn't used.
- Age on this date
- The date to measure the age on. It starts as today's date where you are (your device's time zone). It can't be earlier than the date of birth.
Formula and method
complete months = the largest whole number of months from birth that does not pass the comparison date years = complete months ÷ 12 (whole part); months = the remainder days = comparison date − (birth date + complete months) total days = comparison date − birth date
Age is counted the way people say it out loud: full months first, then the leftover days. Moving forward a whole month keeps the same day of the month. If that day doesn't exist in the next month, the calendar's last day of that month is used instead. So someone born on January 31 completes a month on February 28 (or 29 in a leap year).
February 29 birthdays follow the same rule. In years without a February 29 (common years), the birthday counts on February 28, and the age goes up by one that day. In leap years it falls on February 29 as usual.
The calculator treats dates as whole calendar days, not moments in time. So time zones and daylight-saving changes don't affect the answer. Total weeks are whole weeks, with the leftover days shown beside them.
Worked example
Someone was born on June 15, 1990. How old are they on October 18, 2026?
- From June 15, 1990 to June 15, 2026 is 36 complete years.
- From June 15 to October 15, 2026 is 4 more complete months.
- From October 15 to October 18 is 3 days.
- Counting every day: 13,274 days in total. That's 1,896 weeks and 2 days, or 436 complete months.
- In hours: 13,274 × 24 = 318,576 hours (about 19.1 million minutes).
- The next birthday is June 15, 2027. Count 13 days left in October, then 30 + 31 + 31 + 28 + 31 + 30 + 31 days to May 31, plus 15. That's 240 days.
Result: They are 36 years, 4 months and 3 days old. They were born on a Friday. Their next birthday is in 240 days, on Tuesday, Jun 15, 2027, when they turn 37.
Understanding the result
The completed-years number is your age in the everyday sense. It's the number you put on forms and check against age limits.
Total days and weeks are handy for milestones, like a 10,000-day birthday, or for comparing two ages closely.
The hours and minutes are whole days multiplied out. So they can be off by up to one day (24 hours), depending on the time you were born.
Assumptions and limitations
- Both dates use today's standard (Gregorian) calendar, even for dates before a country switched to it.
- A February 29 birthday counts on February 28 in years that aren't leap years.
- The day you were born doesn't count as a birthday. On that day, the next birthday is one year away.
- The time of day is ignored. Someone born late in the evening counts as a full day older from midnight. That's why the hours and minutes totals are approximate.
- Some laws and organizations have their own rule for February 29 birthdays. For example, some treat March 1 as the birthday in common years. If the exact date matters legally, check which rule applies.
- Not every culture counts age the same way. This calculator counts completed years (full years since birth).
Frequently asked questions
When does someone born on February 29 turn a year older?
In this calculator, on February 28 in common years and on February 29 in leap years. So a person born on February 29, 2000 counts as 1 year old on February 28, 2001. On February 27 they're still 0.
Why does a month sometimes have 28 days and sometimes 31 in the result?
Months are counted as calendar months, not as a set number of days. One month after March 15 is April 15, which is 31 days later. One month after February 15 is March 15, which is 28 or 29 days later.
Does my time zone affect the result?
Only in deciding what today is. The second date starts as today's date where you are. After that, the dates are plain calendar dates, and the math is the same everywhere.
How many days old am I?
Leave the second date on today and read Total days. It counts every calendar day from your birth date up to today, including each February 29 along the way. Someone born on June 15, 1990 is 13,274 days old on October 18, 2026.
How do I find my age on a past or future date?
Change the “Age on this date” field. Say you want to know if someone will be 21 by a trip in May. Enter the trip date, and the completed-years number is the age they'll be that day.
How do I work out an age in months, say for a baby?
Read Total months. It counts full calendar months from the date of birth. So a baby born on March 10 is 2 months old from May 10 until June 9. The leftover days appear in the main years, months and days result.
Is my date of birth stored or shared?
The calculation runs in your browser. This calculator doesn't create a shareable link that contains your date of birth.
How this calculator is checked
Method: Gregorian calendar arithmetic: complete calendar months with end-of-month clamping, then remaining days; day counts from a proleptic Gregorian day number. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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