For dates we use ordinal numbers, so: May 10th or 10th of May. Also for abbreviated dates (xx/xx/xx), we often write month/date/year (might be true just for the US, not sure). For instance, my birthday is 12/28/85 (December 28th, 1985).

Hi Emma, In British English, we write either 10 May or 10th May. There is no need to write "of", although it is included when the date is spoken.