usermod -e

I'm trying to add an expiration to all of the local logins, but everytime I do the:

usermod -e <date> <login>

command, I get a error msg "usermod error <date> is not a valid expiration date. CHoose another"

I've tried 6/26/06, June 26, 2006, 26/6/06, 6/26/2006 everything I can think of.

Any ideas?

According to my manual pages, the format it expects is YYYY-MM-DD.