JSON date to Java date? [duplicate]

Question

I could not find this anywhere. I fetch some JSON from an API that returns standard JSON dates. You can see the format by running this code in a JavaScript console:

> new Date().toJSON();
"2010-10-27T11:58:22.973Z"

Well, actually, the API I'm working with is not returning the millisecond part, and sometimes it returns a timezone instead of Z, so dates can look like any one of these:

• 2010-10-27T11:58:22Z
• 2010-10-27T11:58:22+03:00

Parsing these kinds of dates is somewhat cumbersome. Is there any way to parse these kinds of dates, using org.json?

My current solution is:

public static Date parseDateTime(String dateString) {
    if (dateString == null) return null;
    DateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssZ");
    if (dateString.contains("T")) dateString = dateString.replace('T', ' ');
    if (dateString.contains("Z")) dateString = dateString.replace("Z", "+0000");
    else
        dateString = dateString.substring(0, dateString.lastIndexOf(':')) + dateString.substring(dateString.lastIndexOf(':')+1);
    try {
        return fmt.parse(dateString);
    }
    catch (ParseException e) {
        Log.e(Const.TAG, "Could not parse datetime: " + dateString);
        return null;
    }
}

Ugh!

Answer 1

That DateTime format is actually ISO 8601 DateTime. JSON does not specify any particular format for dates/times. If you Google a bit, you will find plenty of implementations to parse it in Java.

Here's one

If you are open to using something other than Java's built-in Date/Time/Calendar classes, I would also suggest Joda Time. They offer (among many things) a ISODateTimeFormat to parse these kinds of strings.

Answer 2

Note that SimpleDateFormat format pattern Z is for RFC 822 time zone and pattern X is for ISO 8601 (this standard supports single letter time zone names like Z for Zulu).

So new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSX") produces a format that can parse both "2013-03-11T01:38:18.309Z" and "2013-03-11T01:38:18.309+0000" and will give you the same result.

Unfortunately, as far as I can tell, you can't get this format to generate the Z for Zulu version, which is annoying.

I actually have more trouble on the JavaScript side to deal with both formats.

Answer 3

If you need to support more than one format you will have to pattern match your input and parse accordingly.

final DateFormat fmt;
if (dateString.endsWith("Z")) {
    fmt = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
} else {
    fmt = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");
}

I'd guess you're dealing with a bug in the API you're using which has quoted the Z timezone date pattern somewhere...