How is my age calculated?

The calculator counts full calendar years, months, and days between your birthday and the target date (today by default). It uses Luxon — the same date library most accounting and scheduling software relies on — running against the IANA time zone database, so leap years, leap seconds, and historical calendar quirks are all handled correctly. The result is identical to the calculation a court or vital-records office would use to verify your age.

What day of the week was I born?

The tool shows your birth day of week directly — enter your birthday and look for the "Born on" row in the Birth details panel. This is derived from Zeller's congruence applied to the Gregorian calendar (the calendar adopted by most countries between 1582 and 1923). For births before your country adopted the Gregorian calendar, the day of week is still correct per the proleptic Gregorian calendar — the modern mathematical convention.

How many days until my next birthday?

The "Next birthday" panel shows the exact date of your next birthday and the number of days until it. Leap-day birthdays (February 29) are observed on March 1 in non-leap years — matching the most common legal and statistical convention. Some jurisdictions observe February 28 instead; the difference is one day in the count.

Is my birth data stored?

No. The calculator runs entirely in your browser — nothing is sent to a server or saved. Once you close the tab, the date is gone. This is by design: we don't want to be a custodian of birth-date data, and you shouldn't have to trust us with it.

Why does the calculator say I am X years and Y months — not just years?

Because that's how age is actually counted in most legal, medical, and demographic contexts. A child is "18 months old," not "1.5 years." Pediatric, immigration, and legal records all use full-units-plus-remainder. The fractional-year alternative is also displayed ("Total days") for cases where you need a single number.

Can I calculate someone else's age in the past or future?

Yes. Change the target date field to any date — past or future — and the calculator computes age as of that date. This is useful for historical research, planning ceremonies tied to specific ages (bar mitzvah, retirement eligibility, voting age), or curiosity about how old someone famous would be today.

Are there cultural age conventions different from this calculation?

Yes. Traditional East Asian age counting (still used in some Korean and Chinese contexts) starts at one at birth and adds a year at Lunar New Year — so a baby born in December could be considered "two years old" within weeks. South Korea standardized to international age counting in 2023 for official purposes. This calculator uses the international/Western "completed years" convention exclusively.

Age Calculator

Calculate your exact age in years, months, and days — plus total hours, minutes, and seconds alive.

Birth date

Age as of

You are

36 years, 3 months, 0 days

Or 13,260 days total.

Totals since birth

Total days: 13,260
Total hours: 318,240
Total minutes: 19,094,400
Total seconds: 1,145,664,000

Birth details

Born on: Monday
Date: 01 Jan 1990
Zodiac: Capricorn
Week of year: 1

Next birthday

Your next birthday is on Friday, 01 January 2027 — 254 days away.

You'll be 37 years old.

Weekday breakdown

Weekdays: 9,472
Weekend days: 3,788

How the age calculator works

The calculator takes two dates — your birth date and a target date (today by default) — and computes the difference using the IANA time zone database and the Gregorian calendar. It returns full years, months, and remaining days, plus several useful derived numbers: total days alive, total hours, total minutes, day of week you were born, and your next birthday.

The unit of "a year" matters more than people realize. Calendar years are not all the same length: a year that includes February 29 is one day longer than a non-leap year. The calculator handles this correctly by anchoring to actual calendar dates rather than approximating with average year length. If your birthday is February 29, the calculator counts you as turning a year older on March 1 in non-leap years — the most common legal convention.

Why "exact age" usually doesn't matter, and when it does

For most everyday purposes, "I'm 34" is fine. But there are specific contexts where age to the day matters:

Insurance underwriting — life insurance premiums often change at 6-month or "nearest birthday" boundaries. A policy quoted today may price differently than one quoted tomorrow.
Retirement eligibility — early withdrawal from a 401(k) is penalty-free starting the day you turn 59½, not on January 1 of that year. Social Security full retirement age is similarly date-specific.
Driver's license and voting — most states verify age to the day for first-time license issuance and for voter registration deadlines.
Estate planning — minor children become legal adults on their 18th birthday at midnight in their time zone. Trust distributions tied to specific ages are precise to the day.
Pediatric medicine — vaccine schedules, developmental milestones, and medication dosing for young children are tracked in months and days, not years.
Historical research and genealogy — calculating someone's age at a specific event (a marriage, a census date, a death) is the basic operation of family-history research.

Total days, total hours: what those numbers really mean

The "Totals since birth" panel shows total days, hours, minutes, and seconds. These are not trivia — they're useful for several specific things. The number of total days is exactly how Medicare, Social Security, and the IRS measure age for benefit eligibility. The number of total hours is the unit airlines and shipping companies use for crew rest requirements and equipment maintenance intervals. Total seconds is the actual age your computer's clock measures from your birthdate — useful if you need a Unix-style timestamp for a database record or a "born on" age comparison in code.

Weekday vs. weekend breakdown comes up more often than you'd expect: pediatric studies sometimes correlate weekend-born children with different outcomes (mostly confounded), payroll-style "lived workdays" calculations, and historical research asking "did this person have to attend school on their birthday most years?"

Privacy note

Everything runs in your browser. Your birth date doesn't leave your device, isn't logged, and isn't sent anywhere. The calculator works offline once the page has loaded. This is by design — there's no reason a date calculator needs to be a custodian of birth dates, and we'd rather not be.

Last updated: May 21, 2026

Frequently asked questions

How is my age calculated?: The calculator counts full calendar years, months, and days between your birthday and the target date (today by default). It uses Luxon — the same date library most accounting and scheduling software relies on — running against the IANA time zone database, so leap years, leap seconds, and historical calendar quirks are all handled correctly. The result is identical to the calculation a court or vital-records office would use to verify your age.
What day of the week was I born?: The tool shows your birth day of week directly — enter your birthday and look for the "Born on" row in the Birth details panel. This is derived from Zeller's congruence applied to the Gregorian calendar (the calendar adopted by most countries between 1582 and 1923). For births before your country adopted the Gregorian calendar, the day of week is still correct per the proleptic Gregorian calendar — the modern mathematical convention.
How many days until my next birthday?: The "Next birthday" panel shows the exact date of your next birthday and the number of days until it. Leap-day birthdays (February 29) are observed on March 1 in non-leap years — matching the most common legal and statistical convention. Some jurisdictions observe February 28 instead; the difference is one day in the count.
Is my birth data stored?: No. The calculator runs entirely in your browser — nothing is sent to a server or saved. Once you close the tab, the date is gone. This is by design: we don't want to be a custodian of birth-date data, and you shouldn't have to trust us with it.
Why does the calculator say I am X years and Y months — not just years?: Because that's how age is actually counted in most legal, medical, and demographic contexts. A child is "18 months old," not "1.5 years." Pediatric, immigration, and legal records all use full-units-plus-remainder. The fractional-year alternative is also displayed ("Total days") for cases where you need a single number.
Can I calculate someone else's age in the past or future?: Yes. Change the target date field to any date — past or future — and the calculator computes age as of that date. This is useful for historical research, planning ceremonies tied to specific ages (bar mitzvah, retirement eligibility, voting age), or curiosity about how old someone famous would be today.
Are there cultural age conventions different from this calculation?: Yes. Traditional East Asian age counting (still used in some Korean and Chinese contexts) starts at one at birth and adds a year at Lunar New Year — so a baby born in December could be considered "two years old" within weeks. South Korea standardized to international age counting in 2023 for official purposes. This calculator uses the international/Western "completed years" convention exclusively.