field-day
n
1 day on which military operations are practised 军事演习日.
2 day or period of great excitement and activity 振奋人心的重要日子或时期
Whenever there's a government scandal the newspapers have a field-day. 政府一有丑闻, 报界便紧张忙碌一阵.
3 (esp US)
(a) sports day at a school, college, etc （学校等的）体育比赛日, 运动会.
(b) day of outdoor scientific study 野外科研活动日.