[fastball]

Not only is YYYY/MM/DD unambiguous, but it also sorts correctly by date when you perform a naive alphabetical sort.

[LoganDark]

I believe YYYY-MM-DD is even less ambiguous than YYYY/MM/DD.

[a96]

Correct. Slashes mean it's a yank date and going to be backwards. Dashes hint that it's going to be (close to) ISO standard.

[_Algernon_]

And it doesn't use a path-separator character for the date.

[tom_]

Slashes are used for dd/mm/yyyy as well. Dashes are indeed better if you want a separator. or use the separator-free ISO 8601 syntax.

[worik]

I just use the number of peta-seconds since I was born....