wareki

Wareki is the Japanese calendar system used to date years in Japan, based on era names known as nengō. The term wareki combines a word for Japan or traditional Japan (wa) with ki, meaning calendar. In this system, years are counted within a specific era, so dates are often written as Reiwa 3 or Meiji 45.

History and structure: The nengō system originated in ancient Japan and was formalized in the early centuries to denote reigns and important events. An era name is chosen for a period and the year count resets to 1 at the start of each era. While emperors’ reigns commonly determine era boundaries, there have been gaps and changes that produced multiple nengō within a single reign. In the modern era, Japan adopted the Gregorian calendar for civil use during the Meiji period, but wareki remains widely used in government, media, and everyday life, often alongside Western dating.

Modern usage: Since May 1, 2019, the current era is Reiwa, marking the accession of Emperor Naruhito. The previous era was Heisei (1989–2019); earlier eras include Showa (1926–1989) and Taisho (1912–1926). The era name is selected through a government process and publicly announced in advance. In many contexts, dates appear in both wareki and the Western calendar, depending on formality, tradition, and international considerations.

Comparison and notes: Wareki is distinct from seireki, the Western Gregorian calendar, which counts years continuously from AD 1. In Japan, both systems coexist and are used to date documents, calendars, and historical records, with wareki providing continuity with traditional and imperial-era dating.