also: アースデイ
noun
Earth Day (April 22)
Refers specifically to the international environmental event held annually on April 22.
アースデーには各地で環境イベントが開かれる。
On Earth Day, environmental events are held in various places.
Spelling with interpunct; rarely used in practice.
Spelling with interpunct and デイ; rarely used in practice.
Borrowed from English 'Earth Day'.