在英语里几月几号用介词on,那为什么My birthday is May 1st.不用呢

My birthday is May 1st.
这里May1st 是做整句话的表语,不是说是在哪一天,而是说是几月几号.
老师祝你学习进步!
望采纳,多谢!^_^What's the date?It's on July 9th.那为什么用ON不加。What's the date?It's July 9th.I was born on July 9th.就不一样了。