Mostly harmless pet peeve du jour: Date formats.
2007-09-08 – Hooray, this is sortable and unambiguous!
11/10/2011 – Was that a Tuesday or a Thursday?
30 OCT 29 – At least there's time to ask....
10.4.12 – Wait, let me guess—
080907 – oh no
Bonus peeve:
22:15 – Waaaah, I don't understand "military time"!
10:15 – Waaaah, I showed up twelve hours late!