SimpleDateFormat from = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
SimpleDateFormat to = new SimpleDateFormat("MM/dd/yyyy Z");
Date date = from.parse("2017-08-10T00:00:00.000+0000");
String newDateStr = to.format(date);
The newDateStr is 08/09/2017 -0500. I expect that newDataStr can have the same timezone as the original date string(0000) -- 08/10/2017 -0000. What should I do to achieve this?
Preserving the offset from the original string is much easier with java.time, the modern Java date and time API:
DateTimeFormatter from = DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss.SSSZ");
DateTimeFormatter to = DateTimeFormatter.ofPattern("MM/dd/yyyy Z");
String newDateStr = OffsetDateTime.parse("2017-08-10T00:00:00.000+0000", from)
.format(to);
System.out.println(newDateStr);
This prints
08/10/2017 +0000
This is not the only reason for recommending changing to the modern API. The Date class that you are using is long outdated, and SimpleDateFormat in particular is renowned for being troublesome to work with. I always recommend staying away from those classes in 2018. The modern API is generally much nicer. And since you are already using Java 8, there is absolutely no reason why you shouldn’t want it (for anyone reading along and using Java 6 or 7, the new API has been backported to those Java versions too).
An old-fashioned Date object is just a point in time, it doesn’t hold a time zone or offset in it. So after you had parsed your string into a Date, the offset information was no longer there. So neither the Date nor to, the new formatter, had any way of knowing which offset or time zone had been in the original string. Instead, the new formatter used its own time zone. Since you had not explicitly set a time zone on the formatter, its time zone was that of your JVM, which apparently was a time zone that was on offset -5 from UTC on these days of September 2017.
There are tricky ways to solve the problem with the outdated classes, but as I have probably said already, I wouldn’t want to bother.
@Ponomarenko Oleh in a comment writes:
Pay attention: "Call requires API Level 26" for Android.
However, java.time works nicely on both older and newer Android devices. It just requires at least Java 6.
org.threeten.bp with subpackages.java.time was first described.java.time to Java 6 and 7 (ThreeTen for JSR-310).
You could use the Java 8 Date API which provides a good set of functionality to convert dates into strings (including timezone support).
An example:
ZonedDateTime dateTime = ZonedDateTime.parse("2017-08-10T00:00:00.000+0000", DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZ"));
String newDateStr = dateTime.format(DateTimeFormatter.ofPattern("dd/MM/yyyy Z"));
For more information you can look at:
Datedoesn’t have a time zone or offset, so there’s no way to preserve it in what you are doing. See How to set offset of a java.util.Date? Much easier to solve your task withjava.time, the modern Java date and time API.