I always prefer, default to, and advocate for yyyy-MM-dd format for dates to avoid confusion. Once you're used to them, no other format will do. Also, files with such names (backups, etc) will also be in a natural order.
I started to refuse to accept any document that does not have the YYYY-MM-DD format, and time as HH:MM. I also encourage people to use UTC because we work in 130 countries so 15:27 does not make much sense.
I have to work with logs from computers and applications and this is driving me nuts. "What is the timezone ?" is the question everyone fears.
