Example 1
2000-01-01 as birth -> age counted to today.
Age calculator
Pick a date of birth. The calculator subtracts it from today on this device and shows years, leftover months, and leftover days. January 1, 2000 on August 17, 2026 is 26 years, 7 months, and 16 days. The second card is the civil days total from birth, not split into years.
Two dates side by side: difference between dates. Days until an event: countdown to date. Pregnancy: due date.
Result
Enter a value. The result shows up here.
How it works
Calendar age is handwritten subtraction, not milliseconds divided by 365. You subtract the birth year, month, and day from today on this device. If the day has not arrived this month, you borrow days from the previous month. If the month has not arrived, you borrow a year. January 1, 2000 on August 17, 2026 is 26 years, 7 months, and 16 days. May 12, 1990 on that same date is 36 years, 3 months, and 5 days.
February has 29 days in a leap year and 28 in a common year. Someone born on February 29, 2020 and someone born on March 1, 2020 can share the same year count in a common February and still differ on the second card. Leftover days on the first card are the remainder after years and months, not that total.
The second card counts civil days from birth to today. That is a calendar-day gap, with no hours. A March or November clock change does not add or drop a day. May 15 is May 15, whatever time zone the birth was in.
Today comes from the device clock, but only the year, month, and day. A future birth date will not print a negative age. You get a prompt to fix the field. If you do not pick a date, the calculator will not invent a birthday.
Age as on a passport, from the day of birth. We count from the day of birth, the way a passport does. The metric or US switch does not convert years, because years are not kilometers.
When you want the gap between two free dates, not birth to today, open the date-difference page. Days until a chosen event live on the countdown. A pregnancy estimate from a period is a different page, about 280 days, not a child’s age.
How to use
- In the date of birth field, pick a day from the calendar, for example January 1, 2000. The value is year-month-day.
- Click Calculate. Read years, leftover months, and leftover days on the first card.
- The second card shows the civil-day total from birth to today on this device.
- If the date is in the future, fix it. The calculator will not guess a birthday when the field stays empty.
- Two free dates, not necessarily to today, belong on date difference. Days until an event belong on the countdown.
Formula
years, months, days = today − date of birth, with day and month borrow as in handwritten subtraction
Total days = (today − birth) in UTC civil days. Today = the device local date. A future birth date = error.
Years, months, and civil days
Age = today minus date of birth, with day and month borrow. January 1, 2000 on August 17, 2026 is 26 years, 7 months, and 16 days.
- months
- The remainder after whole years. From January 1, 2000 on August 17, 2026 you have 7 months and 16 days, not 26.6 years on a sign.
- civil days
- The second card: the whole gap from birth, not split. February 29 and March 1 can share the years and still differ in the day total.
Real-life examples
Example 2
1990-05-12 fills the field -> years and leftover months to today.
Example 3
2020-02-29 as birth -> age from 29 Feb to today.
Example 4
1975-12-31 fills birth -> age to the date on this device.
Example 5
2010-06-01 as the start of life -> years and months to today.
Example 6
2004-02-29 fills the field -> age from a leap day.
Example 7
2024-12-31 as birth -> infant age counted to today.
Example 8
1988-03-15 fills birth -> full calendar age to today.
Ways to use this calculator
- You check a child’s or a senior’s age on a form when the record only has a birth date, not a ready year count.
- You compare someone born on February 29 with someone born on March 1, because the years can match while the day total does not.
Frequently asked questions
How old is someone born January 1, 2000 on August 17, 2026?
26 years, 7 months, and 16 days. The second card shows the civil days total from that birth to that day, not only the leftover after years.
How is the day total different from leftover days on the first card?
Leftover days are the remainder after years and months, here 16 after 26 years and 7 months. The day total is the whole civil gap from January 1, 2000, not split into years.
How do you treat February 29 next to March 1?
Both dates can show the same age in years in a common February. The civil days total on the second card still differs, because February 29, 2020 exists and February 29, 2021 does not.
Where does “today” come from?
From this device’s local date: year, month, and day, with no hour. January 1, 2000 on August 17, 2026 is 26 years, and after midnight on August 18 the leftover days move on their own.
What if the birth date is in the future?
The calculator asks you to fix it and will not show a negative age. Tomorrow’s date instead of January 1, 2000 does not give −1 year.
Does a spring or fall clock change move the result?
No. We count civil days, not hours. 26 years, 7 months, and 16 days from January 1, 2000 stay put, and turning the clock does not add a birthday.
Is this Korean age with plus one at birth?
No. We count from the day of birth, the way most documents do after 2023. January 1, 2000 on August 17, 2026 is 26 years, not 27 from the start.
Where do I count the gap between two free dates?
On date difference. There January 1, 2024 to January 1, 2025 is 366. Here one date is always today, and the other is the birth date.
Will February 30 go through?
The browser usually will not let you pick it. A pasted day that does not exist, unlike February 29, 2020, gets an error and does not count years.
Where are days until a wedding or an exam, not age?
On the countdown to a date. There the target is in the field, and the start is today. Here the result is years, months, and days from January 1, 2000, not only the days until a party.
Knowledge sources
Day counts and age follow the Gregorian calendar. This is date arithmetic, not a time-zone tool.
Page updated in 2026.