May first, or the first of may is fine even if you see it written as May 1st.

It doesn't help that the day-month order is different between English speaking countries. ;) Stick with the order you see. So: "May 1st" is "May the first", or simply "May first". "1 May" is "the first of May" (sometimes written as "1st May", but that's a little confusing - the first May of how many Mays?? Better to write "the 1st of May").

Ｂａｓｉｃａｌｌｙ　ｂｏｔｈ　ａｒｅ　ｃｏｒｒｅｃｔ．Ｂｕｔ　ｉｆ　ｙｏｕ　ａｒｅ　ｒｅａｄｉｎｇ　ａ　ｄａｔｅ　ｙｏｕ　ｓａｙ　”Ｍａｙ　ｆｉｒｓｔ，ｔｗｏ　ｔｈｏｕｓａｎｄ　ｔｅｎ”　 ”Ｆｉｒｓｔ　ｏｆ　Ｍａｙ”　ｍａｙ　ｂｅ　ｕｓｅｄ　ｌｉｋｅ　”Ｉｔ　ｗａｓ　ｔｈｅ　ｆｉｒｓｔ　ｏｆ　Ｍａｙ　ｗｈｅｎ　．．．”

It's 'May first', man! Today is October, nineteen, two thousand ten =)