The Emperor's Birthday

The Emperor's Birthday (天皇誕生日, Tennō tanjōbi) is a national holiday in the Japanese calendar celebrated on 23 December of each year. The date is determined by the reigning Emperor's birthdate. Emperor Akihito was born on 23 December 1933.

During the reign of Emperor Hirohito (Shōwa period, 1926–1989), the Emperor's birthday was observed on 29 April. That date remained a public holiday, posthumously renamed Greenery Day in 1989 and Shōwa Day in 2007.

Prior to World War II, it was called Tenchōsetsu (天長節), "Tenchō Festival". Tenchōsetsu paralleled Chikyūsetsu (地久節), "Chikyū Festival", which referred to the Empress consort's birthday. The two names originate from the Chinese chengyu 天長地久, borrowed during the reign of Emperor Kōnin, meaning "long heaven, lasting earth" and expressed a hope for the longevity of the reigning Emperor. After the war, the new government renamed it to Tennō tanjōbi, in less formal language with a more literal meaning in 1948, when it was established as a holiday by law. Under the law, the National Diet must convene and change the holiday date before the reigning Emperor's birthday becomes a public holiday. Thus, there exists a small chance that the former Emperor's birthday may come before the change can be made.

On 23 December, a public ceremony takes place at the Imperial Palace, where the gates of the palace are opened to public traffic (the Imperial Palace is usually off limits to the public). The Emperor, accompanied by the Empress, and several other members of the Imperial Family appear on a palace balcony to acknowledge the birthday congratulations of crowds of festive well-wishers waving tiny Japanese flags. Only on this occasion and on 2 January may the general public enter the inner grounds of the Imperial Palace.

When the Emperor ceases his greeting, the crowd starts waving the flags again and the Imperial Family wave back.