How old are you, exactly?

Nine calendars, nine different answers for the same person. Put in a birth date and see all of them at once, each with its working shown.

Date of birth

Time

Place of birth

If you do not know the time, noon changes only the hours and seconds. The place sets the time zone your birth instant is read in, which is what every calendar below is computed from — 27,000+ cities from the GeoNames gazetteer.

Observances 厄年 for men · Bar Mitzvah 厄年 for women · Bat Mitzvah

The calculation runs entirely in your browser: nothing is sent anywhere, nothing is stored, and no cookie is set. The only place a birthdate is written down is the address bar — which is what makes a link shareable.

JavaScript is off, so the form above cannot compute. Everything below is a complete worked example demonstrating the calculations for someone born 1 January 2000 in London, calculated when this page was built on 29 September 2026. Every reference table on this site works without JavaScript too — the links under each heading go to the explanations.

Gregorian, completed: 26 years, 8 months, 28 days 1 h 15 m 40 s
Time lived: 9,768 days 843,956,140 seconds
Next birthday: 1 January 2027 — a Friday, turning 27
On Mars you would be: 14.219 Mars years One orbit is 687 Earth days.

Nine calendars, nine answers

Computed as of 29 September 2026. Where a calendar cannot answer for a date, it says so and gives the reason rather than extrapolating.

Worked example: age by reckoning system for someone born 1 January 2000 in London. Every row names its own system, so it still means something quoted on its own — and South Korea contributes three rows because it uses three counts at once.
Calendar	Age today	When the count turns over
Gregorian	26 years, 8 months, 28 days	On the anniversary of the birth instant.
만 나이 (international age) — Korea, legal	26	On the birthday. Used on all civil, judicial and administrative documents since 28 June 2023.
세는나이 (Korean age) — Korea, traditional	27	One at birth, and a year added for everyone on 1 January.
연 나이 (year age) — Korea	26	Calendar year minus birth year. Military service and age-restricted sales use this.
虚岁 (nominal age) — China	28	One at birth, and a year added at Lunar New Year.
数え年 (counted age) — Japan	27	One at birth, and a year added for everyone at New Year.
tuổi mụ (nominal age) — Vietnam	28	One at birth, and a year added at Tết.
Hijri — Umm al-Qura	27 years, 6 months, 23 days	On the Hijri birthday. A lunar year is eleven days shorter, which compounds into a whole year every thirty-three.
Hebrew	26 years, 8 months, 24 days	On the Hebrew birthday; a leap month keeps the year in season.
Solar Hijri — Jalali	26 years, 8 months, 27 days	On the birthday; a solar year, so this tracks the Gregorian count. The year itself begins at Nowruz.

And, not a calendar at all

Every figure above answers “which year of life are you in” or “how long since you were born”. This one just divides elapsed time by how long another planet takes to go round the Sun.

**Planetary orbits** — Not a calendar: elapsed time divided by each planet’s sidereal orbital period, from the NASA fact sheets. How this is worked out
Mercury ☿	111.039 Mercury years 111 complete orbits; the current one has 85 Earth days to run.
Venus ♀	43.471 Venus years 43 complete orbits; the current one has 119 Earth days to run.
Earth ♁	26.743 Earth years 26 complete orbits; the current one has 94 Earth days to run.
Mars ♂	14.219 Mars years 14 complete orbits; the current one has 537 Earth days to run.
Jupiter ♃	2.255 Jupiter years 2 complete orbits; the current one has 3,230 Earth days to run.
Saturn ♄	0.908 Saturn years 0 complete orbits; the current one has 992 Earth days to run.
Uranus ♅	0.318 Uranus years 0 complete orbits; the current one has 20,918 Earth days to run.
Neptune ♆	0.162 Neptune years 0 complete orbits; the current one has 50,421 Earth days to run.
Pluto ♇	0.108 Pluto years 0 complete orbits; the current one has 80,792 Earth days to run.

Each system in full

The same figures with everything the summary leaves out, and beside each one the convention it applies or the limit it has reached.

**Gregorian** — The civil calendar, counted from the exact instant of birth in the birthplace’s time zone. How this is worked out
Completed age	26 years, 8 months, 28 days
And, since your last whole day	1 h 15 m 40 s Counting from the time of day you were born.
Days lived	9,768 days
Seconds lived	843,956,140 seconds Elapsed seconds, which pass at the same rate in every calendar on this page.
In decimal years	26.743905 years Elapsed time divided by the Gregorian mean year of 365.2425 days.
Born on a	Saturday
Western zodiac sign	Capricorn ♑ — Earth The sun sign for Dec 22 – Jan 19. A correspondence, not a reading.
Next birthday	1 January 2027 — a Friday, turning 27

**Korean** — Three counts used at once in South Korea, two of which ignore your birthday. How this is worked out
세는나이 (se-neun nai) — Korean age	27 One at birth, and a year added for everyone on 1 January.
연 나이 (yeon nai) — year age	26 Calendar year minus birth year. Military service and age-restricted sales use this.
만 나이 (man nai) — international age	26 Since 28 June 2023, South Korea has used 만 나이 (international age) on all civil, judicial and administrative documents. By the traditional count you are 27; the legal age is 26.

**Chinese** — Nominal age and the zodiac both turn at Lunar New Year, not on 1 January. How this is worked out
虚岁 (xūsuì) — nominal age	28 One at birth, and a year added at Lunar New Year.
周岁 (zhōusuì) — completed age	26
Lunar date of birth	25th day of the 11th month, lunar year 1999 From the Hong Kong Observatory conversion tables.
Sexagenary year and zodiac	己卯 (Ji-Mao) — Yin Earth Rabbit The year you were born into, which begins at Lunar New Year.
Next Lunar New Year	6 February 2027 — lunar year 2027 begins, the year of the Fire Goat 130 days away. Your 虚岁 (nominal age) goes up that day.

**Japanese** — The modern count, the traditional one, and the imperial era you were born into. How this is worked out
数え年 (kazoedoshi) — counted age	27 One at birth, and a year added for everyone at New Year.
満年齢 (mannenrei) — completed age	26
Imperial era of birth	平成12年 (Heisei 12) Today is 令和8年 (Reiwa 8).
厄年 (yakudoshi) — critical year, this year	No Counted in 数え年 (counted age). The ages differ by gender and by shrine.
年祝い (toshi-iwai) — celebration of a long life	None at this age

**Vietnamese** — The two Vietnamese counts, from Vietnam’s own lunisolar calendar. How this is worked out
Tuổi mụ — nominal age	28 One at birth, and a year added at Tết.
Tuổi thực — completed age	26
Lunar date of birth	25th day of the 11th month, lunar year 1999 Computed from Vietnam’s own lunisolar tables, on the 105°E meridian rather than China’s 120°E. That year the two calendars agreed.
Can chi year	Kỷ Mão The year you were born into, which begins at Tết.
Next Tết Nguyên Đán	6 February 2027 — năm Đinh Mùi begins 130 days away. Your tuổi mụ goes up that day.

**Hijri** — The Umm al-Qura calendar. A lunar year is about eleven days shorter than a solar one. How this is worked out
Hijri date of birth	24 Ramadan 1420 AH A Hijri day begins at sunset; this is the civil day.
Hijri age	27 years, 6 months, 23 days
Against the Gregorian count	27 Hijri years against 26 Gregorian — 1 year ahead Eleven days a year, which compounds into a whole year every thirty-three.
Next Hijri birthday	3 March 2027 — turning 28 155 days away.

**Hebrew** — Twelve months in most years, thirteen in seven years out of nineteen. How this is worked out
Hebrew date of birth	23 Tevet 5760 A Hebrew day begins at sunset; this is the civil day.
Hebrew age	26 years, 8 months, 24 days
Year of birth	A leap year, with two months of Adar
Bar Mitzvah	5 January 2013 — at 13 Hebrew years The Hebrew birthday, not thirteen solar years on.

**Solar Hijri** — A solar calendar whose year begins at the vernal equinox. How this is worked out
Solar Hijri date of birth	11 Dey 1378 AP
Solar Hijri age	26 years, 8 months, 27 days A solar year, so this tracks the Gregorian count.
Next Nowruz	21 March 2027 — 1406 AP begins 173 days away.

Why the answers differ

A solar calendar counts the Earth going round the Sun; a lunar one counts the moon going round the Earth, and twelve of those fall eleven days short of a year. A lunisolar calendar inserts a thirteenth month to close the gap.

And four of the counts above are not measuring elapsed time at all — 세는나이, 虚岁, 数え年 and tuổi mụ start at one and advance for everybody on the same day, so they answer which year of life are you in rather than how long have you been alive. None of these is a rounding of the others.

The pages below explain each one, and each carries a worked example computed when the page was built — so they are readable, and checkable, without running anything.

The nine calendars

Korean age — South Korea counts age three ways. What each one is, which documents use which, and what changed on 28 June 2023 — with worked examples.
Chinese age — Nominal age advances at Lunar New Year, not on your birthday, and so does the zodiac animal. The two counts, the sexagenary year, and where the tables stop.
Japanese age — Counted age (kazoedoshi) and completed age (mannenrei), the imperial era of a birth date to the day, the critical years (yakudoshi), and the celebrations of a long life.
Vietnamese age — The two Vietnamese counts, the can chi year, Tết as the boundary — and an honest account of which calendar this site computes them from.
Hijri age — A Hijri year is about eleven days shorter than a solar one, so a Hijri age runs ahead and a Hijri birthday walks backwards through the seasons. What that means, in dates.
Hebrew age — Twelve months in most years and thirteen in seven years out of nineteen. What that does to a birthday in Adar, when a Bar or Bat Mitzvah falls, and where sunset comes into it.
Persian age — A solar calendar whose year begins at the vernal equinox, with six months of 31 days. Your Solar Hijri birth date, your age in it, and the Gregorian date of Nowruz.
Planetary age — Elapsed time since birth divided by each planet’s orbital period, from the NASA fact sheets — and an honest account of why this is not a calendar.
Earth age — Tropical, sidereal, anomalistic, draconic, Julian and Gregorian mean year lengths, the three rotation periods of the Earth, and your age in each — with why none of them agree.

Reference tables

Data rather than prose: dates and boundaries that are true regardless of who is reading, and that can be quoted on their own.

Lunar New Year dates — The Gregorian date of Lunar New Year for every year from 1901 to 2099, with the sexagenary year and zodiac animal it begins, from the Hong Kong Observatory tables.
Tết dates — The Gregorian date of Tết for every year from 1901 to 2099, from Vietnam’s own lunisolar tables, with the seven years it falls away from Chinese Lunar New Year.
Japanese eras — The Gregorian start and end date of every imperial era from Meiji to Reiwa, to the day, with the rule that makes the first year of an era gannen (元年) rather than year 1.
Sexagenary cycle — Ten heavenly stems against twelve earthly branches: all sixty combinations in order, with element, zodiac animal, Vietnamese can chi and the years each one names.
Yakudoshi ages — The critical-year (yakudoshi) ages observed at most Shinto shrines, counted in traditional counted age, with the years before and after each and the Gregorian years each one falls in.
Longevity celebrations — Kanreki through Hyakuju — the age each falls at in both counts, the colour, and the pun on the written numeral that gives each celebration its name.
Calendar months — The months of each calendar in order and in its own script, with the lengths they take and a note on the two that do not have a fixed number of months.

Date converters

A different question from the one above: not how old you are, but what a given date is called in another calendar. Both directions on one page, and every answer says which authority it came from.

Hijri dates — Convert a Gregorian date to the Hijri calendar and a Hijri date back again, either way, from 1583 to 2562 — Umm al-Qura where it is tabulated and the tabular Islamic calendar, named as such, outside it.

Research notes

Longer investigations into how these calendars are computed and where the authorities part company, each with its data and its limits.

When the new moon falls near midnight: ICU’s Chinese calendar against the Hong Kong Observatory — Day by day from 1901 to 2100, where the Chinese calendar built into JavaScript parts from the Hong Kong Observatory, what causes each disagreement, and the three months this century that no one can yet date.

How this site treats your dates

Nothing is stored, sent anywhere, or measured. There is no account, no database and no server that sees your birthdate: the calculation above runs entirely in your browser, and the only place a date is written down is the address bar, if you choose to copy the link.

Every figure states its method and where it stops being reliable, and the about page collects all of that in one place — including the ranges each calendar is published for and what happens outside them.