My geeky system datetime format: longnow variant ISO8601 dates with ordinal day of year:
Protip: leave out the longnow preceding 0 in the short/medium formats as otherwise the created/modified datetimes in the Finder column view will be truncated to just the date by default.
Emil Björklund:
Take a look at the diagram I just retweeted. Ambiguous date formats annoy me... Just use ISO, please. It's easy: falling granularity, Y-m-d.
@thatemil RRRR yes, ambiguous date formats are so stupid, especially when they’re on tickets (british rail, I’m looking at you)