The former Emperor marked his 90th birthday on the 23rd, which is a major celebration in Japan.
ご質問ありがとうございます。
・「The former Emperor marked his 90th birthday on the 23rd, which is a major celebration in Japan.」
(意味)上皇さまは23日に卒寿の90歳をむかえた。これは日本で大きなお祝い事です。
・Emperor 天皇
・celebrationお祝い
・birthday誕生日
参考になれば幸いです。