The story happened______the morning of May 1,2009,应该填什么介词呀?都具体到天了填on对吗?或者是填at?因为出现了早上这个时间点.给理由

用ON,在（某一天）用ON：on the evening of May the first
on your birthday
on Tudesdays
参考：牛津高阶英汉双解词典P1199

The story happened___on___the morning of May 1,2009
是的，具体到天填on

具体到某一天或某一天的上午、下午或晚上,要用介词 on

记住，以下内容对中考和高考非常有用，要仔细阅读和背出来：
in January
in winter
in 1999;
in the morning/ afternoon /evening.
in the daytime
on Monday,
on Sunday afternoon,
on July 1st, 2011
at six o’clock,
at three thirty.
at night,
at noon,
at this time of year.
in a year
in spring
in September
in a week ,
in two weeks
in two weeks' time
on Monday
on Monday afternoon
on March 7th, 2000
at eight o’clock
at this time of day /year
at the moment
in the summer / winter holiday
at Christmas
on Christmas Day / Eve / afternoon
on the evening of May 31st,2011
on National Day
on Children's Day
on the day of my arrival / departure
on the day she comes
in the year I was born
on the very Monday she fell ill
on Thanksgiving Day
during our stay in Japan
in Tom's absence
in the presence of my friends
on our way to the library
on their first trip to Shanghai
on a voyage inthe Atlantic Ocean