How the Age Calculator Works
Your age is the time that has passed since you were born. The Age Calculator counts it from your date of birth to today, or to any other date that you choose, and gives it in years, months and days, as well as in the total number of months, weeks, days and hours.
What you enter
- The date of birth.
- The date to calculate the age on. It is today's date at the start. Choose a day in the past to find an age at a past event, or a day in the future to find how old you will be.
How the age is counted
- The whole years and months. The calculator finds the largest number of whole months that fit between the two dates. Twelve months are one year, so 436 months is 36 years and 4 months.
- The days that are left. It adds those whole months to the date of birth, and counts the days from there to the date. These are the days of the age.
- The total days. It counts the whole days between the two dates, including all the leap days.
When a month is shorter than the day of the birth (for example, born on 31 January, and one month later is February), the date is moved back to the last day of that month. This means that the age does not become negative or jump, as it can when the days are borrowed from the month before.
Worked example: born 15 May 1990, on 25 September 2026
| Result | Value |
|---|---|
| Age | 36 years, 4 months, 10 days |
| Total months | 436 |
| Total weeks | 1,897 weeks and 3 days |
| Total days | 13,282 |
| Total hours | 318,768 |
| Born on a | Tuesday |
| Next birthday | Saturday, May 15, 2027, in 232 days |
The hours are the days times 24. They do not include the time of the day that you were born, and they are not the exact number of hours that you have lived.
Your year of life
The calculator draws a bar from your last birthday to your next one. In the example, 133 days of the 365 have passed since 15 May 2026, which is 36%. Each block is 2.5% of the year.
████████████████████████████████████████ Last birthday (15 May 2026) 133 of 365 days (36%) Next birthday (15 May 2027)
Milestones in days
Round numbers of days are easy to celebrate. For a person who was born on 15 May 1990, these are the dates when they reach them. Each block is 750 days.
| Days old | About | Date |
|---|---|---|
| 1,000 days | 2.7 years | Monday, February 8, 1993 |
| 5,000 days | 13.7 years | Thursday, January 22, 2004 |
| 10,000 days | 27.4 years | Saturday, September 30, 2017 |
| 15,000 days | 41.1 years | Monday, June 9, 2031 |
| 20,000 days | 54.8 years | Wednesday, February 15, 2045 |
| 25,000 days | 68.4 years | Friday, October 25, 2058 |
| 30,000 days | 82.1 years | Sunday, July 3, 2072 |
1,000 days █ 2.7 years 5,000 days ███████ 13.7 years 10,000 days █████████████ 27.4 years 15,000 days ████████████████████ 41.1 years 20,000 days ███████████████████████████ 54.8 years 25,000 days █████████████████████████████████ 68.4 years 30,000 days ████████████████████████████████████████ 82.1 years
The weekday of a birthday
A birthday moves one day of the week later each year, and two days after a leap year has passed (because 365 days are 52 weeks and 1 day, and 366 days are 52 weeks and 2 days). For the birthday of 15 May:
| Year | 15 May is a |
|---|---|
| 2026 | Friday |
| 2027 | Saturday |
| 2028 | Monday |
| 2029 | Tuesday |
| 2030 | Wednesday |
| 2031 | Thursday |
Born on 29 February
A person who is born on 29 February has a real birthday only in a leap year, which is every four years. In the other years, the calculator counts the birthday on 28 February. The age changes to the next year on that day, and the days until the next birthday are counted to it. Some countries use 1 March by law, and the rule depends on where you are.
Why the time zone does not change the age
A date of birth is a calendar date and has no time zone. The calculator works on whole calendar days, so you get the same answer in every country, and the day is not moved by an hour of difference.
Tips
- Age on a past date: for example, to find the age at a graduation or a wedding, change the second date.
- Age of a child: the age in months is often used until the age of two or three.
- Legal ages: the age for a right (to vote, to drive, to retire) is counted from the birthday. Check the rule for your country.
What this calculator does not include
- The time of day of the birth, and the exact number of hours, minutes and seconds.
- Ages by other calendars, or a lunar age (used in some parts of East Asia, where a child is one year old at birth).
- Dates before the year 1, or after the year 9999.
This tool is for general information. For a legal or official age, use your official documents.