Japanese Era Converter

How Japanese era dates work, and where conversions go wrong

Japan counts years in two ways. Alongside the Gregorian calendar it uses wareki (和暦): the name of the current era followed by the year within it. The current era is Reiwa (令和), so a date in 2025 is written Reiwa 7. Government forms, tax slips, pension notices, municipal certificates and many company documents still use era years first. Japan Pension Service forms go a step further and number the eras, asking for a date of birth after an era code: 5 for Shōwa, 7 for Heisei, 9 for Reiwa. The arithmetic looks trivial: find the era, subtract. It is trivial everywhere except the places that matter, which are the changeovers.

Four changeovers, each set by its own instrument

The first surprise is that the modern eras did not all start the same way. When the Meiji emperor died on 30 July 1912, the edict issued that day declared that "from 30 July Meiji 45 onward" the year was Taishō 1, so 30 July 1912 is the first day of Taishō, not the last day of Meiji. The edict issued when the Taishō emperor died on 25 December 1926 used the same wording, which is why Shōwa 1 lasted only seven days.

Since 1979, eras have been set under the Era Name Act (元号法) by cabinet order, and each order names the day it takes effect. The order naming Heisei was promulgated on 7 January 1989, the day the Shōwa emperor died, and took effect "from the day after promulgation", so 7 January 1989 is the last day of Shōwa 64 and Heisei 1 began on 8 January. Reiwa was announced on 1 April 2019. Its order took effect on the day after the abdication law's effective day of 30 April, and under that law the new emperor acceded at once, so Reiwa began on 1 May 2019, the day of accession. Heisei began the day after an accession and Reiwa on one. No single rule, "the day of accession" or "the day after", reproduces all four changeovers. A converter needs the four dates themselves, and a day is precisely what a date of birth or a contract start date cannot afford.

30 July 1912 is the first day of Taishō, but 7 January 1989 is the last day of Shōwa. Heisei began the day after an accession; Reiwa began on one.

Dates an era never reached

The second surprise is that some real documents carry dates that never existed. Anything written before May 2019 that looked further ahead than April could name a date such as 平成32年3月31日, Heisei 32, because nobody knew when Heisei would end. There was never a Heisei 32; by the time that year arrived it was Reiwa 2. Statutes are the clearest case. The law for the international exposition of 2025 was promulgated on 26 April 2019, four days before Heisei ended, with 平成三十七年 in its title, and its implementing ordinance still carried that Heisei title on e-Gov, Japan's official law database, on 2 October 2026. That day e-Gov's current texts of 302 laws and regulations in force contained a Heisei year the era never reached, from 32 to 72. The latest, 平成七十二年三月三十一日, 31 March 2060, is in a cabinet order on the Kansai and Osaka airports; many others are spent transitional provisions rather than live deadlines. For government documents the question is settled: the ministries' liaison conference on the era change agreed on 1 April 2019 that a Heisei year in a ministry's own documents stays valid for dates after the change, and that applications to ministries written that way are accepted. The meaning is not in doubt either way: counted forward, Heisei 32 is 2020. This tool treats such a date as what it is, a date written beyond the era's last day, and gives you both the Gregorian date and the era that day actually fell in, rather than rejecting it.

Why nothing before 1873 converts day-for-day

Japan did not use the Gregorian calendar until 1873. Under a proclamation of late 1872, the day that would have been the third day of the twelfth month of Meiji 5 was declared to be 1 January Meiji 6. Every date written before that, including the first five years of Meiji, is a lunisolar date, and a lunisolar month does not line up with a Gregorian one. By the National Astronomical Observatory of Japan's tables, Meiji 2 ran from 11 February 1869 to 31 January 1870. "Meiji 3, 4th month, 10th day" was 10 May 1870, not the 10 April 1870 that arithmetic gives, so the tool refuses the day and says which lunisolar year it fell in. The year table lists 1868 to 1872 with the Gregorian day each lunisolar year began. Converters also differ on where Meiji starts: the 1868 edict, issued on 23 October 1868, applied the name from the lunar new year of 25 January, which is the date used here, while software built on the ICU date library starts Meiji on the day of the edict. No day before 1873 is converted here either way.

Why it matters in Southeast Asia

Many of the people who meet wareki dates are not Japanese. Japan's labour ministry counted 2,571,037 foreign workers at the end of October 2025, and Vietnam was the largest nationality at 605,906 (Ministry of Health, Labour and Welfare, 「外国人雇用状況」の届出状況, end of October 2025). The three fastest-growing nationalities were Myanmar (up 42.5%), Indonesia (up 34.6%) and Sri Lanka (up 28.9%); the Philippines, third-largest at 260,869, grew 6.2% against 11.7% overall. A worker returning to Hanoi, Manila or Jakarta brings home pay slips, withholding-tax statements (源泉徴収票, headed by a Reiwa year), pension notices and resident-record certificates, and an HR team or a pension-refund agent in the region has to read the dates on them correctly. Japanese companies across ASEAN issue the same documents to their own staff. For all of them the boundary cases above are not trivia: an employment start date in the first week of 1989 or the last days of April 2019 is exactly where a one-day slip happens.

The forms you will see written

The same date can appear half a dozen ways. In full kanji the first year of an era is written 元年 (gannen) rather than 1, and statutes write the numbers in kanji too: 平成三十一年四月三十日. Forms and software often reduce the era to one letter, M, T, S, H or R, as in H31.04.30 for the last day of Heisei. Unicode also carries a single "square era name" character for each era; the one for Reiwa, ㋿ (U+32FF), was the only character added in Unicode 12.1.0, released in May 2019. It sits apart from the other four (U+337B to U+337E) because the next code point was already taken. The panel above shows your date in every one of these forms.