SimpleDateFormat ignores “XXX” if timezone is set to “UTC”

问题

I am trying to output the current datetime as UTC in the following format: 2016-01-11T14:08:42+00:00

final SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXXX");
formatter.setTimeZone(TimeZone.getTimeZone("UTC"));

final String dateString = formatter.format(new Date());

"dateString" should now contain "2016-01-11T14:08:42+00:00" but it contains "2016-01-11T14:08:42Z".

Without the "UTC" timezone setting I get the right format but - of course - in my specific timezone...

Any ideas?

回答1:

See the documentation for SimpleDateFormat:

For formatting [using an ISO 8601 Time zone], if the offset value from GMT is 0, "Z" is produced.

So, this behaviour is expected.

You can either:

• Use the RFC 822 timezone formatter ZZZ; however, this produces "+0000"
• Manipulate the string to replace the final Z: str.replaceAll("Z$", "+00:00")

来源：https://stackoverflow.com/questions/34723683/simpledateformat-ignores-xxx-if-timezone-is-set-to-utc