Japanese Era Converter

Converting between Japanese era years and the Gregorian calendar isn't just year arithmetic — the transition dates matter. Showa only runs through January 7, 1989; January 8 is already Heisei 1. This tool anchors conversion to the exact transition date of each era (Meiji, Taisho, Showa, Heisei, Reiwa), so boundary dates convert correctly. Converting AD to era just needs a date picker; converting era to AD takes an era, year, month, and day. Year 1 of an era displays as 元 (gannen). Dates before Meiji, or era/year/month/day combinations that fall outside that era's actual span, are reported as errors.