Age Calculator & Era Converter

How to use

1. Under “Age calculator”, enter your date of birth to see your exact age (years, months, days), counting ages, zodiac sign, the weekday you were born and a countdown to your next birthday.
2. “Calculate age on” starts at today in your time zone. Change it to see your age on another day; press “Today” to go back.
3. Under “Year converter”, choose an input type (Western year, ROC year or a Japanese era) and type a year to see the Western year, ROC year, Japanese era, zodiac, stem-branch name and that year's Lunar New Year.
4. To check the era or zodiac for one specific day, choose “Exact date (to the era change day)” as the input type.
5. Open the age chart at the bottom to see this year's age for every birth year at a glance.

Worked example

Born before Lunar New Year: someone born on January 20, 2000 is 26 years, 8 months and 25 days old on October 15, 2026. Lunar New Year 2000 fell on February 5, so their sign is the Rabbit (Ji-Mao), not the Dragon. Their Chinese nominal age is 28 and their Korean counting age is 27.

Other results for the same birthday: they were born on a Thursday, have lived 9,765 days, and their next birthday is January 20, 2027, 97 days away, when they turn 27.

Era conversion: entering the year 2019 shows “Heisei 31 / Reiwa 1 (era began May 1, 2019)”, ROC year 108 in Taiwan, the Year of the Pig (Ji-Hai), and Lunar New Year on February 5, 2019.

Reading the results

• Your exact age goes up by one on each birthday. This is the age used in law and on documents in most countries, including Korea since June 28, 2023.
• Counting ages start at 1 at birth. The Chinese nominal age (xusui) adds a year at each Lunar New Year; Korean and Japanese counting age adds a year every January 1. Either one is 1 to 2 years more than your exact age.
• Zodiac signs change at Lunar New Year, not on January 1. Anyone born before that year's Lunar New Year belongs to the previous sign. Some astrologers switch at Lichun (around February 4) instead; this tool does not.
• When you enter only a year in which the Japanese era changed, both eras are listed. Pick “Exact date (to the era change day)” to see which era a specific day belongs to.

How it works

• Exact age counts from the day of birth. Someone born on February 29 turns a year older on March 1 in common years, matching the rule in Taiwan's Civil Code and Japan's Act on Calculation of Ages that a period ending in a month without the matching day ends on the last day of that month.
• Chinese nominal age = the lunar year of the target date − the lunar year of birth + 1, where any date before Lunar New Year belongs to the previous lunar year. Lunar New Year dates for 1900–2100 are built in, checked year by year from 1901 against the Hong Kong Observatory's Gregorian–Lunar calendar tables.
• Zodiac and stem-branch: (year − 4) mod 12 gives the animal and (year − 4) mod 10 gives the heavenly stem, since 4 CE was a Jia-Zi year of the Rat. For example, 2026 is Bing-Wu, the Year of the Horse.
• Japanese eras switch on the day of the change: Taisho July 30, 1912, Showa December 25, 1926, Heisei January 8, 1989 and Reiwa May 1, 2019. The first year of an era is year 1 (gannen). Meiji is counted from the start of 1868 by convention. ROC year = Western year − 1911.

Limitations

• Dates (birthday, target date) work from January 1, 1900 to December 31, 2100; year conversion covers 1868–2100.
• The tool converts years and ages only. It does not show lunar month and day, solar terms or astrology charts.
• Before 1873 Japan used a lunisolar calendar, so month and day in Japanese era dates from that time differ from Western dates. Only the year is converted.
• Legal ages for drinking, school entry, insurance or military service follow their own rules. Check the rules that apply to you.

FAQ

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