题目

英文：星期几 前 一定要加 ON
China to announce recruitment plan for women astronauts
The Chinese government will announce a plan to choose the country's first female astronaut at the end of this year,the Beijing News reported Monday.
Taiwan mudslide may have buried 600 villagers
A mudslide triggered by torrential rains from a typhoon may have buried up to 600 villagers in mountainous southern Taiwan,disaster officials said on Monday.
为什么第一段结尾的Monday前没加ON,而第二段结尾的Monday前加了ON.区别是什么,什么情况下,星期几前可以不加ON.

提问时间：2020-05-07

答案

第一段 中省略了ON,因为是一篇新闻报道,在新闻报道中,体现时间、地点、人物等要素的时候,为了简练、清晰,可以省略相应的副助词
第二段中比较严谨,是个完整的句子
这样的情况不必深究,只要自己理解了就行