In the past, when working with others in the office, I used the yy-mm-dd format, and like it a lot. Now that I work mostly by myself, and use the lisp routines I write, by myself, I have gotten lazy and use the dd-mm-yy format. After reading this, I might go back to the yy-mm-dd format, or as Michael pointed out yyyy-mm-dd format which will take away all confusion.