Reputation: 3496
there are two string
String date = "9/13/2012";
String time = "5:48pm";
the time is GMT+0, I wanna change it to GMT+8,what is the simplest way to change a time to particular timezone
Upvotes: 0
Views: 214
Reputation: 79620
The java.util
Date-Time API and their formatting API, SimpleDateFormat
are outdated and error-prone. It is recommended to stop using them completely and switch to the modern Date-Time API*.
Also, quoted below is a notice from the home page of Joda-Time:
Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.
Solution using java.time
, the modern Date-Time API:
import java.time.LocalDateTime;
import java.time.OffsetDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
public class Main {
public static void main(String[] args) {
String date = "9/13/2012";
String time = "5:48pm";
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("M/d/u h:ma", Locale.UK);
LocalDateTime ldtSource = LocalDateTime.parse(date + " " + time, dtf);
OffsetDateTime odtSource = ldtSource.atOffset(ZoneOffset.UTC);
OffsetDateTime odtTarget = odtSource.withOffsetSameInstant(ZoneOffset.of("+08:00"));
System.out.println(odtTarget);
// In a custom format
System.out.println(odtTarget.format(dtf));
}
}
Output:
2012-09-14T01:48+08:00
9/14/2012 1:48am
Learn more about the modern Date-Time API from Trail: Date Time.
* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.
Upvotes: 1
Reputation: 5192
The Joda-Time library provides a good set of objects for working with dates/times in multiple time zones. http://joda-time.sourceforge.net/
Something like this for example:
String date = "9/13/2012";
String time = "5:48pm";
String[] dateParts = date.split("/");
Integer month = Integer.parseInt(dateParts[0]);
Integer day = Integer.parseInt(dateParts[1]);
Integer year = Integer.parseInt(dateParts[2]);
String[] timeParts = time.split(":");
Integer hour = Integer.parseInt(timeParts[0]);
Integer minutes = Integer.parseInt(timeParts[1].substring(0,timeParts[1].lastIndexOf("p")));
DateTime dateTime = new DateTime(year, month, day, hour, minutes, DateTimeZone.forID("Etc/GMT"));
dateTime.withZone(DateTimeZone.forID("Etc/GMT+8"));
Upvotes: 1
Reputation: 1504182
SimpleDateFormat
set to the UTC time zoneDate
value using a SimpleDateFormat
set to the time zone you're interested in. (It's likely to be something other than just "UTC+8" - you should find out which TZDB time zone ID you really want.For example:
SimpleDateFormat inputFormat = new SimpleDateFormat("MM/dd/yyyy h:mma", Locale.US);
inputFormat.setTimeZone(TimeZone.getTimeZone("Etc/UTC");
Date date = inputFormat.parse(date + " " + time);
// Or whatever format you want...
SimpleDateFormat outputFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm", Locale.US);
outputFormat.setTimeZone(targetTimeZone);
String outputText = outputFormat.format(date);
(If you can use Joda Time instead, that'd be great - but I understand that it's pretty big for an Android app.)
Upvotes: 2