Day set for the beginning of a large-scale military operation.

【军】攻击发动日。

A day on which an important operation or planned action is to begin.

重要工作的开始日。

June 6, 1944, the day of the invasion of German-occupied Europe by the Allies.

诺曼地登陆日；二次世界大战中盟军开始攻击德国占领之欧陆之日(一九四四年六月六日)。

Decimal day, the day when Britain changed its currency and measuring systems into decimal systems.

十进日(英国将货币及度量衡制改为十进制的日子)。