I routinely do this in emails and documents. No one has ever questioned me on it because they're used to it from folder/file names.

Please do join me in slowly changing the world over to year, month, day order.

(Though I prefer the non-standard dots instead of hyphens, as they are non-line-breaking, and allows for hyphens to be used as separators for other parts in a file along with underscores)

YYYY.MM.DD is my fave