These were completely missing because I forgot about them... I added sorting functionality before I added date functionality, but it turns out I didn't even need the datetime library to do this!
However, this implementation feels incomplete. If you sort by the accessed date, it still displays the modified date, so the dates still look out of order. If I were to change the date column for the user, though, then there would still be no header to signify that the column has changed. I'm not sure how to proceed with this, but this is still missing functionality, so in it goes.
This makes it more like ls. The --long (-l) argument has been added to get at the old behaviour, and the --links argument is now on -H. I can't crib this behaviour from ls because it shows it by default.
TODO: The terminal size is currently assumed to be 80, and it uses the string length, rather than the width.
