The era name of Emperor Hirohito’s reign when Japan surrendered in 1945 was Shōwa.
Hirohito became emperor in 1926, beginning the Shōwa era, which lasted until his death in 1989. Japan surrendered during the middle of that era, after the atomic bombings of Hiroshima and Nagasaki and the Soviet declaration of war against Japan.
“Shōwa” is often written “Showa” in English without the macron. The name means “enlightened peace,” although the period included militarization, empire-building, World War II, occupation, and Japan’s postwar economic reconstruction.
The other era names are from different reigns. Meiji preceded Taishō, while Heisei began in 1989 under Hirohito’s son, Akihito. Hirohito is also known posthumously as Emperor Shōwa, following Japan’s one-reign, one-era-name convention.