Where did mm/dd/yyyy come from?

One of the hypotheses is that the United States borrowed the way it was written from the United Kingdom who used it before the 20th century and then later changed it to match Europe (dd-mm-yyyy). American colonists liked their original format and its been that way ever since.

What is YYYY-MM-DD format example?

Date and Time FormatsFormat SpecifierFormatExample%d/%m/%ydd/mm/yy21/02/18%d-%m-%Ydd-mm-yyyy21-02-2018%d-%m-%ydd-mm-yy21-02-18%m-%d-%Ymm-dd-yyyy02-21-201821 more rows