How can I change the format of a date from the command line?

Question

What\'s the quickest way to convert a date in one format, say

2008-06-01

to a date in another format, say

Answer 1

If you're just looking to get the day of the week, don't try to match strings. That breaks when the locale changes. The %u format give you the day number:

 $ date -j -f "%Y-%m-%d" "2008-01-03" +"%u"
 4

And indeed, that was a Thursday. You might use that number to index into an array you have in your program, or just use the number itself.

See the date and strftime man pages for more details. The date manpage on OS X is the wrong one, though, since it doesn't list these options that work.