将任何时区的日期和时间转换为 UTC 区域

Question

• this is my date " 15-05-2014 00:00:00 "

• how to convert IST to UTC ie( to 14-05-2014 18:30:00)

• based on from timezone to UTC timezone.

my code is

DateFormat formatter = new SimpleDateFormat("dd MMM yyyy HH:mm:ss");

formatter.setTimeZone(TimeZone.getTimeZone("IST"));  //here set timezone

System.out.println(formatter.format(date));  
formatter.setTimeZone(TimeZone.getTimeZone("UTC"));  //static UTC timezone

System.out.println(formatter.format(date));  
String str = formatter.format(date);
Date date1  = formatter.parse(str);
System.out.println(date1.toString());

• if user enter same date from any zone then will get UTC time(ex: from Australia then 15-05-2014 00:00:00 to 14-05-2014 16:00:00)

• please any suggestions.

Answer 1

You cannot "convert that date values" to other timezones or UTC. The type java.util.Date does not have any internal timezone state and only refers to UTC by spec in a way which cannot be changed by user (just counting the milliseconds since UNIX epoch in UTC timezone leaving aside leapseconds).

But you can convert the formatted String-representation of a java.util.Date to another timezone. I prefer to use two different formatters, one per timezone (and pattern). I also prefer to use "Asia/Kolkata" in your case because then it will universally works (IST could also be "Israel Standard Time" which will be interpreted differently in Israel):

DateFormat formatterIST = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
formatterIST.setTimeZone(TimeZone.getTimeZone("Asia/Kolkata")); // better than using IST
Date date = formatterIST.parse("15-05-2014 00:00:00");
System.out.println(formatterIST.format(date)); // output: 15-05-2014 00:00:00

DateFormat formatterUTC = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
formatterUTC.setTimeZone(TimeZone.getTimeZone("UTC")); // UTC timezone
System.out.println(formatterUTC.format(date)); // output: 14-05-2014 18:30:00

// output in system timezone using pattern "EEE MMM dd HH:mm:ss zzz yyyy"
System.out.println(date.toString()); // output in my timezone: Wed May 14 20:30:00 CEST 2014

Answer 2

tl;dr

LocalDateTime.parse( 
    "15-05-2014 00:00:00" , 
    DateTimeFormatter.ofPattern( "dd-MM-uuuu HH:mm:ss" ) 
)
.atZone( ZoneId.of( "Asia/Kolkata" ) )
.toInstant()

java.time

The Answer by Meno Hochschild is correct but shows classes that are now outdated.

DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd-MM-uuuu HH:mm:ss" ) ;
LocalDateTime ldt = LocalDateTime.parse( "15-05-2014 00:00:00" , f ) ;

ldt.toString(): 2014-05-15T00:00

Apparently you are certain that string represents a moment in India time. Tip: You should have included the zone or offset in that string. Even better, use standard ISO 8601 formats.

Assign the India time zone.

ZoneId z = ZoneId.of( "Asia/Kolkata" ) ;
ZonedDateTime zdt = ldt.atZone( z ) ;

zdt.toString(): 2014-05-15T00:00+05:30[Asia/Kolkata]

To see the same moment, the same point on the timeline, through the wall-clock time of UTC, extract an Instant .

Instant instant = zdt.toInstant() ;

instant.toString(): 2014-05-14T18:30:00Z

---

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date , Calendar , & SimpleDateFormat .

The Joda-Time project, now in maintenance mode , advises migration to the java.time classes.

To learn more, see the Oracle Tutorial . And search Stack Overflow for many examples and explanations. Specification is JSR 310 .

With a JDBC driver complying with JDBC 4.2 or later, you may exchange java.time objects directly with your database. No need for strings or java.sql.* classes.

Where to obtain the java.time classes?

• Java SE 8 , Java SE 9 , and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport .
• Android
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP… .

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval , YearWeek , YearQuarter , and more .