SimpleDateFormat not properly handling 12 a.m

Question

I'm trying to parse the string "2/20/2012 12:00:00 AM" using SimpleDateFormat, and it seems to be coming out 12 p.m. instead.

    Date fromFmt = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss aa")
                       .parse("2/20/2012 12:00:00 AM");

    // Calendar months are 0-indexed
    Date fromCal = new Date(new GregorianCalendar(2012, 1, 20, 0, 0, 0)
                       .getTimeInMillis());

    System.out.println(fromFmt);
    System.out.println(fromCal);

outputs:

Mon Feb 20 12:00:00 PST 2012
Mon Feb 20 00:00:00 PST 2012

I would expect both of them to output the latter. Is there something wrong with my format string?

(And please nobody say 'use JodaTime'.)

Answer 1

Use this instead:

new SimpleDateFormat("MM/dd/yyyy hh:mm:ss aa")

Notice I'm using hh instead of HH. The former does this:

Hour in am/pm (1-12)

HH does this:

Hour in day (0-23)

---

You're telling the SimpleDateFormat that you're going to pass in an hour in the 0-23 range, but you're not actually doing that. That's why you get this issue.