Using DateFormat.getDateTimeInstance().format(date);

Question

When running some tests I came across the following issue. When using:

private String printStandardDate(Date date) {
    return DateFormat.getDateTimeInstance(
        DateFormat.SHORT, DateFormat.SHORT).format(date);
}

I found this produced different formats of Date depending on the location the tests where run from. So locally in windows / eclipse I got a result: 04/02/12 18:18 but on the Linux box in America I get 2/4/12 6:18 PM

This causes my Tests/Build to fail:

expected:<[04/02/12 18:18]> but was:<[2/4/12 6:18 PM]>

Could anyone explain this behavior?

Answer 1

That's not strange, that's exactly how it's supposed to work.

The API documentation of DateFormat.getDateTimeInstance says:

Gets the date/time formatter with the given date and time formatting styles for the default locale.

The default locale is different on your Windows system than on the Linux box in America.

If you want exact control over the date and time format, use SimpleDateFormat and specify the format yourself. For example:

private String printStandardDate(Date date) {
    return new SimpleDateFormat("dd/MM/yy HH:mm").format(date);
}

Even better would be to re-use the SimpleDateFormat object, but beware that it is not thread-safe (if the method might be called from multiple threads at the same time, things will get messed up if those threads use the same SimpleDateFormat object).

private static final DateFormat DATE_FORMAT =
    new SimpleDateFormat("dd/MM/yy HH:mm");

private String printStandardDate(Date date) {
    return DATE_FORMAT.format(date);
}