Japanese Era Calendar Dates with Intl.DateTimeFormat

Japanese Era Calendar Formatting

Japan uses a unique calendar system based on Imperial eras. The current era is Reiwa (令和), which began on May 1, 2019. The Intl.DateTimeFormat API supports this calendar through the -u-ca-japanese Unicode extension.

Basic Japanese Era Formatting

const date = new Date('2025-03-15');

new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  dateStyle: 'full',
}).format(date);
// "令和7年3月15日土曜日"

new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  dateStyle: 'long',
}).format(date);
// "令和7年3月15日"

new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  dateStyle: 'medium',
}).format(date);
// "令和7年3月15日"

Era Display Options

new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  era: 'long',
  year: 'numeric',
  month: 'long',
  day: 'numeric',
}).format(date);
// "令和7年3月15日"

new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  era: 'short',
  year: 'numeric',
}).format(date);
// "令和7年"

new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  era: 'narrow',
  year: 'numeric',
}).format(date);
// "R7年"

Japanese Era Timeline

Era	Japanese	Start Date	End Date
Reiwa	令和	2019-05-01	Present
Heisei	平成	1989-01-08	2019-04-30
Shōwa	昭和	1926-12-25	1989-01-07
Taishō	大正	1912-07-30	1926-12-24
Meiji	明治	1868-10-23	1912-07-29

Cross-Era Formatting

// Heisei era date
const heisei = new Date('2018-06-15');
new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  dateStyle: 'long',
}).format(heisei);
// "平成30年6月15日"

// Showa era date
const showa = new Date('1985-03-01');
new Intl.DateTimeFormat('ja-JP-u-ca-japanese', {
  dateStyle: 'long',
}).format(showa);
// "昭和60年3月1日"

Using in English with Japanese Calendar

new Intl.DateTimeFormat('en-US-u-ca-japanese', {
  era: 'long',
  year: 'numeric',
  month: 'long',
  day: 'numeric',
}).format(new Date('2025-03-15'));
// "March 15, 7 Reiwa"

This is useful for applications that need to show the Japanese era in English-language contexts.