Lets say I have a string that represents a date that looks like this:
"Wed Jul 08 17:08:48 GMT 2009"
So I parse that string into a date object like this:
DateFormat formatter = new SimpleDateFormat("EEE MMM dd HH:mm:ss ZZZ yyyy");
Date fromDate = (Date)formatter.parse(fromDateString);
That gives me the correct date object. Now I want to display this date as a CDT value.
I've tried many things, and I just can't get it to work correctly. There must be a simple method using the DateFormat class to get this to work. Any advice? My last attempt was this:
formatter.setTimeZone(toTimeZone);
String result = formatter.format(fromDate);
Use "zzz" instead of "ZZZ": "Z" is the symbol for an RFC822 time zone.
DateFormat formatter = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy");
Having said that, my standard advice on date/time stuff is to use Joda Time, which is an altogether better API.
EDIT: Short but complete program:
import java.text.*;
import java.util.*;
public class Test
{
public List<String> names;
public static void main(String [] args)
throws Exception // Just for simplicity!
{
String fromDateString = "Wed Jul 08 17:08:48 GMT 2009";
DateFormat formatter = new SimpleDateFormat
("EEE MMM dd HH:mm:ss zzz yyyy");
Date fromDate = (Date)formatter.parse(fromDateString);
TimeZone central = TimeZone.getTimeZone("America/Chicago");
formatter.setTimeZone(central);
System.out.println(formatter.format(fromDate));
}
}
Output: Wed Jul 08 12:08:48 CDT 2009
Using:
formatter.setTimeZone(TimeZone.getTimeZone("US/Central"));
outputs:
Wed Jul 08 12:08:48 CDT 2009
for the date in your example on my machine. That is after substituting zzz for ZZZ in the format string.
Sorry for digging out an old-thread. But I was wondering if there is a java-class that holds all the time-zone-ids as a constant class.
So instead of having to hard-code the time-zone-id while setting time-zone like this:
formatter.setTimeZone(TimeZone.getTimeZone("US/Central"));
we would instead be doing something more standard/uniform:
formatter.setTimeZone(TimeZone.getTimeZone(SomeConstantClass.US_CENTRAL));
where SomeConstantClass.java is a class that holds the constants referring to the different time-zone-ids that are supported by the TimeZone class.
The modern way is with the java.time classes.
ZonedDateTime
Specify a formatting pattern to match your input string. The codes are similar to SimpleDateFormat but not exactly. Be sure to read the class doc for DateTimeFormatter. Note that we specify a Locale to determine what human language to use for name of day-of-week and name of month.
String input = "Wed Jul 08 17:08:48 GMT 2009";
DateTimeFormatter f = DateTimeFormatter.ofPattern ( "EEE MMM dd HH:mm:ss z uuuu" , Locale.ENGLISH );
ZonedDateTime zdt = ZonedDateTime.parse ( input , f );
zdt.toString(): 2009-07-08T17:08:48Z[GMT]
We can adjust that into any other time zone.
Specify a proper time zone name in the format of continent/region. Never use the 3-4 letter abbreviation such as CDT or EST or IST as they are not true time zones, not standardized, and not even unique(!).
I will guess that by CDT you meant a time zone like America/Chicago.
ZoneId z = ZoneId.of( "America/Chicago" );
ZonedDateTime zdtChicago = zdt.withZoneSameInstant( z );
zdtChicago.toString() 2009-07-08T12:08:48-05:00[America/Chicago]
Instant
Generally best to work in UTC. For that extract an Instant. The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).
This Instant class is a basic building-block class of java.time. You can think of ZonedDateTime as an Instant plus a ZoneId.
Instant instant = zdtChicago.toInstant();
instant.toString(): 2009-07-08T17:08:48Z
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, & java.text.SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to java.time.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8 and 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 SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
See How to use….
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.
Related
This question already has answers here:
want current date and time in "dd/MM/yyyy HH:mm:ss.SS" format
(11 answers)
display Java.util.Date in a specific format
(11 answers)
DateTimeParse Exception
(2 answers)
Closed 2 years ago.
My source date type is EEE MMM dd HH:mm:ss zzz yyyy. For example, Sat Dec 12 00:00:00 KST 2020 But my target date type is Java Date type with format yyyy-MM-dd. So I make the method which convert Java String type EEE MMM dd HH:mm:ss zzz yyyy to java util object.
private static Date getDate(String beforeDate) throws Exception{
SimpleDateFormat readFormat = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy", Locale.US);
Date rdate = readFormat.parse(beforeDate);
SimpleDateFormat writeFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.US);
String format = writeFormat.format(rdate);
System.out.println(format);
return writeFormat.parse(format);
}
System.out.println(format) line prints the right values which I expect.
2020-12-12
2020-12-12
2013-01-01
But the type of return values is wrong. The return value from the method seems not to be influenced.
System.out.println(getDate("Sat Dec 12 00:00:00 KST 2020"));
The above line prints Sat Dec 12 00:00:00 KST 2020 again. I have no idea which codes are wrong in converting Java date type.
tl;dr
ZonedDateTime
.parse(
"Sat Dec 12 00:00:00 KST 2020" ,
DateTimeFormatter
.ofPattern( "EEE MMM dd HH:mm:ss zzz uuuu" )
.withLocale( Locale.US )
)
.toLocalDate()
.toString()
2020-12-12
Avoid legacy date-time classes
You are using terrible date-time classes that were supplanted years ago by the modern java.time classes. Never use Date, Calendar, or SimpleDateFormat.
You said:
my target date type is Java Date type with format yyyy-MM-dd.
Apparently, you expect Date to hold a date. It does not. The java.util.Date class represents a moment, a date with time-of-day as seen in UTC. The java.sql.Date class pretends to hold only a date, but it too actually contains a date with time-of-day as seen in UTC.
Among the many problems with java.util.Date class is the behavior of its toString method. That method dynamically applies the JVM’s current default time zone while generating text. This anti-feature may contribute to your confusion.
LocalDate
Instead you should be using java.time.LocalDate to represent a date-only value without a time-of-day and without a time zone or offset-from-UTC.
ZonedDateTime
First use the DateTimeFormatter class to parse your entire input string. This results in a ZonedDateTime object representing a moment as seen through the wall-clock time used by the people of a particular region.
Example code
String input = "Sat Dec 12 00:00:00 KST 2020" ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "EEE MMM dd HH:mm:ss zzz uuuu" ).withLocale( Locale.US ) ;
ZonedDateTime zdt = ZonedDateTime.parse( input , f ) ;
From that ZonedDateTime object, extract a LocalDate.
LocalDate localDate = zdt.toLocalDate() ;
See this code run live at IdeOne.com.
zdt.toString(): 2020-12-12T00:00+09:00[Asia/Seoul]
ld.toString(): 2020-12-12
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.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes. Hibernate 5 & JPA 2.2 support java.time.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 brought some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android (26+) bundle implementations of the java.time classes.
For earlier Android (<26), a process known as API desugaring brings a subset of the java.time functionality not originally built into Android.
If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….
I have an variable called data, and it has today's date as in this format: Thu May 24 13:14:41 BRT 2018. Then I format it to MySQL's Date type format, which is yyyy-MM-dd. This code does it:
String dataFormatada = new SimpleDateFormat("yyyy-MM-dd").format(data);
What I want to do is to bring it back to Date type. I've tried somethings but they didn't work. The main solution is to do as discribed in this other Stack Overflow's questioin, and with a little mod I got to what's suposely what I want:
String target = "Thu Sep 28 20:29:30 JST 2000";
DateFormat df = new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH);
Date result = df.parse(target);
System.out.println(result);
But it doesn't work as I get this error when trying to parse:
java.text.ParseException: Unparseable date: "Thu Sep 28 20:29:30 JST 2000"
So I cannot just reformat the data variable, and I cannot bring dataFormatada back to Date format. How do I bring dataFormatada to Date type formatted as yyyy-MM-dd?
Your target String format is in EEE MMM dd HH:mm:ss zzz yyyy format. So you need to use EEE MMM dd HH:mm:ss zzz yyyy as pattern instead of yyyy-MM-dd.
String target = "Thu Sep 28 20:29:30 JST 2000";
DateFormat df = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy", Locale.ENGLISH);
Date result = df.parse(target);
System.out.println(result);
And if you want convert Date object i.e result to yyyy-MM-dd then please use the below code.
DateFormat dfDateToStr = new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH);
String formattedDate = dfDateToStr.format(result);
System.out.println("Formatted Date String : "+formattedDate);
You need two formator, one to parse the orginal string to Date object, one to format it to desired string:
public static void main(String[] args) throws Exception {
String target = "Thu Sep 28 20:29:30 JST 2000";
DateFormat parser = new SimpleDateFormat("EEE MMM dd kk:mm:ss z yyyy", Locale.ENGLISH);
Date result = parser.parse(target);
System.out.println(result);
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
String dataFormatada = format.format(result);
}
tl;dr
For a SQL-standard DATE column, use the java.time.LocalDate class with JDBC 4.2 or later.
myPreparedStatement.setObject(
… ,
ZonedDateTime.parse( // Represent a moment in a particular time zone.
"Thu May 24 13:14:41 BRT 2018".replace( "BRT" , "Europe/London" ) ,
DateTimeFormatter.ofPattern( "EEE MMM d HH:mm:ss z uuuu" , Locale.UK )
)
.toLocalDate() // Extract a date-only value, without time-of-day and without time zone.
)
ISO 8601
I have an variable called data, and it has today's date as in this format: Thu May 24 13:14:41 BRT 201
This is a terrible format. When exchanging date-time values as text, use only the standard ISO 8601 formats. Conveniently, the java.time classes use these formats by default when parsing/generating strings.
BST = ?? (Brazil Standard Time, British Standard Time, … )
Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as BST or IST as they are not true time zones, not standardized, and not even unique(!).
The ZonedDateTime class will try to guess the intended time zone. But you should not be relying on guesses in your code.
String input = "Thu May 24 13:14:41 BRT 2018";
DateTimeFormatter f = DateTimeFormatter.ofPattern( "EEE MMM d HH:mm:ss z uuuu" , Locale.UK );
ZonedDateTime zdt = ZonedDateTime.parse( input , f );
2018-05-24T13:14:41-03:00[America/Sao_Paulo]
Looks like java.time guessed you meant Brazil Standard Time by BST. If you meant some other zone such as British time, replace that BST string by a proper time zone name.
Specify Locale to determine (a) the human language for translation of name of day, name of month, and such, and (b) the cultural norms deciding issues of abbreviation, capitalization, punctuation, separators, and such.
String input = "Thu May 24 13:14:41 BRT 2018".replace( "BRT" , "Europe/London" );
DateTimeFormatter f = DateTimeFormatter.ofPattern( "EEE MMM d HH:mm:ss z uuuu" , Locale.UK );
ZonedDateTime zdt = ZonedDateTime.parse( input , f );
2018-05-24T13:14:41+01:00[Europe/London]
LocalDate
You apparently care about only the date. So extract a date-only object, a LocalDate.
LocalDate ld = zdt.toLocalDate() ;
Smart objects, not dumb strings
Do not exchange date-time values with your database as text. Instead use JDBC and objects. As of JDBC 4.2 and later, you can directly exchange java.time objects with your database.
myPreparedStatement.setObject( … , ld ) ;
Retrieval.
LocalDate ld = myResultSet.getObject( … , LocalDate.class ) ;
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.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, 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 (<26), 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.
I am working with date strings that need to be converted to java.util.date objects.
I'm using the following code to do this:
public void setDates(String from, String to) throws ParseException
{
Date fromDate = new Date();
Date toDate = new Date();
SimpleDateFormat df = new SimpleDateFormat("dd/MM/yyyy");
fromDate = df.parse(from);
toDate = df.parse(to);
this.setDepartDate(fromDate);
this.setReturnDate(toDate);
}
The problem is that the string values that I have to convert are always(And I have no control over this) in the following format: "20 September, 2013".
This causes my function to through a ParseException when it reaches fromDate = df.parse(from);
Could anyone help me understand why, and perhaps suggest a solution?
Check out the SimpleDateFormat JavaDocs for the available format options, but basically, you need to change your date format to something more like dd MMMM, yyyy
try {
String dateValue = "20 September, 2013";
SimpleDateFormat df = new SimpleDateFormat("dd MMMM, yyyy");
Date date = df.parse(dateValue);
System.out.println(date);
} catch (ParseException exp) {
exp.printStackTrace();
}
Which outputs...
Fri Sep 20 00:00:00 EST 2013
As per the javadoc use following format
SimpleDateFormat df = new SimpleDateFormat("dd MMMMM, yyyy");
Also decide if this parsing needs to be Lenient or not and if it needs to be strict use setLenient(false)
By default, parsing is lenient: If the input is not in the form used
by this object's format method but can still be parsed as a date, then
the parse succeeds. Clients may insist on strict adherence to the
format by calling setLenient(false).
Also note that SimpleDateFormat is not threadsafe. If there is a choice I recommend using Joda Time Library that provide much enhanced functionality.
You wrote
[...] in the following format: "20 September, 2013".
Then your SimpleDateFormat should be
"dd MMM, yyyy"
You can check out the SimpleDateFormat documentation.
When you parse a date, you need to know some context or use some assumptions. You can use SimpleDateFormat, but you may need to pre-parse the string to see which format it is before you use it. You may have to try multiple format to see if one or more way to parse the date.
BTW is 01/02/30 the 1st Feb 1930 or 2nd Jan 2030 or 30th feb 2001, you need to know something about what the date is likely to mean or have some control over the format.
LocalDate
The modern approach uses the java.time classes that supplanted the troublesome old date-time classes (Date, Calendar, etc.) years ago.
String input = "20 September, 2013" ;
Locale locale = Locale.US ; // Determines the human language and cultural norms used in parsing the input string.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "d MMMM, uuuu" , locale ) ;
LocalDate ld = LocalDate.parse( input , f ) ;
See this code run live at IdeOne.com.
ld.toString(): 2013-09-20
ZonedDateTime
If you want a time-of-day with that date, such as the first moment of the day, you must specify a time zone. A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.
If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment during runtime(!), so your results may vary. Better to specify your [desired/expected time zone][2] explicitly as an argument.
Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" ) ;
Apply that ZoneId to get a ZonedDateTime. Never assume the day starts at 00:00:00. Anomalies such as Daylight Saving Time (DST) mean the day may start at another time such as 01:00:00. Let java.time determine the first moment of the day.
ZonedDateTime zdt = ld.atStartOfDay( z ) ;
Instant
To adjust into UTC, extract an Instant.
Instant instant = zdt.toInstant() ;
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.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, 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 (<26), 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.
You need to use following date pattern, dd MMMM, yyyy
Try this code,
String dateValue = "20 September, 2013";
// Type of different Month views
SimpleDateFormat sdf = new SimpleDateFormat("dd MMMM, yyyy"); //20 September, 2013
SimpleDateFormat sdf1 = new SimpleDateFormat("dd MM, yyyy"); //20 09, 2013
SimpleDateFormat sdf2 = new SimpleDateFormat("dd MMM, yyyy"); //20 Sep, 2013
Date date = sdf.parse(dateValue); // returns date object
System.out.println(date); // outputs: Fri Sep 20 00:00:00 IST 2013
This question already has answers here:
Java Date Error
(8 answers)
Closed 4 years ago.
String that I want to parse:
Sun Nov 10 10:00:00 CET 2013
My code:
substrings = "Sun Nov 10 10:00:00 CET 2013"
SimpleDateFormat parserSDF = new SimpleDateFormat("EEE MMM d HH:mm:ss ZZZ yyyy");
Date date = parserSDF.parse(substrings);
Compiler error output:
java.text.ParseException: Unparseable date: "Sun Nov 10 10:00:00 CET 2013"
at java.text.DateFormat.parse(Unknown Source)
...
Probably you are missing the correct Locale. Try this, in your example:
SimpleDateFormat parserSDF = new SimpleDateFormat("EEE MMM d HH:mm:ss ZZZ yyyy", Locale.US);
ZZZ will attempt to format the time zone in accordance to RFC 822 time zone, use zzz instead.
Here's the JavaDoc link for reference
java.time
The modern approach uses the java.time classes.
String input = "Sun Nov 10 10:00:00 CET 2013";
DateTimeFormatter f = DateTimeFormatter.ofPattern( "EEE MMM d HH:mm:ss z uuuu" , Locale.US );
ZonedDateTime zdt = ZonedDateTime.parse( input , f );
zdt.toString(): 2013-11-10T10:00+01:00[Europe/Paris]
The terrible old java.util.Date class was replaced years ago by the java.time.Instant class. Both represent a moment in UTC. To adjust from the time zone seen above to UTC, simply extract a Instant object.
Instant instant = zdt.toInstant() ; // Adjust from time zone to UTC.
Avoid java.util.Date. But if you must interoperate with old code not yet updated to java.time, you can convert back and forth. See the new methods added to the old classes, such as Date.from and Date::toInstant methods.
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.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - 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
Most 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 (<26), 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.
The problem is that parserSDF takes a string rather than an array and a ParsePosition. I wrote this to output what I think you want.
import java.text.*;
public class Parser{
public static void main(String[] args){
String input = "Sun Nov 10 10:00:00 CET 2013";
SimpleDateFormat parserSDF = new SimpleDateFormat("EEE MMM d HH:mm:ss ZZZ yyyy");
System.out.println(parserSDF.parse(input, new ParsePosition(0)));
}
}
I recommend taking a look at SimpleDateFormat and ParsePosition within the API
I understand that java Date is timezoneless and trying to set different timezone on Java Calendar wouldn't convert date to an appropriate Time Zone. So I have tried following code
public static String DATE_FORMAT="dd MMM yyyy hh:mm:ss";
public static String CURRENT_DATE_STRING ="31 October 2011 14:19:56 GMT";
DateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println(dateFormat.parseObject(CURRENT_DATE_STRING));
but it outputs wrong date Mon Oct 31 16:19:56 when it must be 12:19:56?
The main issue here is your date format string is using hh (12-hour clock) instead of HH (24-hour)
Secondly, your date format should specify that your date string contains the timezone.
(Alternatively you could uncomment the commented line, to tell it the correct timezone).
Thirdly, you should use a DateFormat to output the time to screen aswell...
Finally, UTC = GMT, so the UTC time is also 14:19:56
(GMT, 'British Winter Time', is the same as UTC, whereas BST is one hour ahead)
public class DateFormatTest {
public static String DATE_FORMAT="dd MMM yyyy HH:mm:ss z";
public static String CURRENT_DATE_STRING ="31 October 2011 14:19:56 GMT";
public static void main(String[] args) throws ParseException {
DateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
//dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
Date d= dateFormat.parse(CURRENT_DATE_STRING);
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println(dateFormat.format(d));
}
}
Output: 31 Oct 2011 14:19:56 UTC
HTH
tl;dr
On that date, at that time, in some eastern Europe time zones, the clocks were running two hours ahead of UTC. So the hour of 14 in UTC (GMT) will appear as 16 (not 12) in zones such as Europe/Helsinki.
ZonedDateTime
.parse
(
"31 October 2011 14:19:56 GMT" ,
DateTimeFormatter.ofPattern
(
"dd MMMM uuuu HH:mm:ss z" ,
Locale.US
)
)
.withZoneSameInstant
(
ZoneId.of( "Europe/Helsinki" )
)
.toString()
2011-10-31T16:19:56+02:00[Europe/Helsinki]
java.time
I understand that java Date is timezoneless
Actually, a java.util.Date represents a moment as seen in UTC, an offset of zero hours-minutes-seconds.
Beware of Date::toString. That terrible toString method dynamically applies the JVM’s current default time zone while generating its text. This creates an illusion of that time zone having been part of the object. One of many reasons to never use this class.
trying to set different timezone on Java Calendar wouldn't convert date to an appropriate Time Zone
You should be using the modern java.time classes, never Calendar. Specifically, use ZonedDateTime to represent a moment as seen through the wall-clock time used by the people of a particular region (a time zone).
"31 October 2011 14:19:56 GMT";
Your input of "31 October 2011 14:19:56 GMT" does not match your formatting pattern "dd MMM yyyy hh:mm:ss". That pattern fails to account for the offset of your input, an offset of zero hours-minutes-seconds indicated by the GMT at the end.
Firstly, do not exchange date-time values using such formats. Learn to use ISO 8601 standard formats for exchanging date-time values as text. The java.time classes conveniently use these standard formats by default when parsing/generating text, so no need to specify a pattern at all.
But if you must parse that particular input string of yours, define a formatting pattern to match.
String input = "31 October 2011 14:19:56 GMT";
Locale locale = Locale.US;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd MMMM uuuu HH:mm:ss z" , locale );
ZonedDateTime zdt = ZonedDateTime.parse( input , f );
Notice how we specified a Locale, to determine the human language and cultural norms used in translation of your input.
EEST – Eastern European Summer Time
Apparently you want to view this moment as seen in the time zone of eastern Europe. I will arbitrarily choose one of the several time zones in that area.
Be aware that EEST is not a real time zone. Specify a proper time zone name in the format of Continent/Region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 2-4 letter abbreviation such as EST or IST or EEST as they are not true time zones, not standardized, and not even unique(!).
ZoneId zoneHelsinki = ZoneId.of( "Europe/Helsinki" );
ZonedDateTime zdtHelsinki = zdt.withZoneSameInstant( zoneHelsinki );
Dump to console.
System.out.println( "zdt = " + zdt );
System.out.println( "zdtHelsinki = " + zdtHelsinki );
zdt = 2011-10-31T14:19:56Z[GMT]
zdtHelsinki = 2011-10-31T16:19:56+02:00[Europe/Helsinki]
Notice how the hour changed from 14 to 16 because at that moment the clocks in Finland were running two hours ahead of UTC.
but it outputs wrong date Mon Oct 31 16:19:56 when it must be 12:19:56?
No the hour 14 is in UTC. Eastern Europe runs ahead of UTC, not behind it. As seen above, Finland on that day was running two hours ahead, so the little hand on the clocks of Finland were pointing at 4 (16 hour) rather than 12.
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.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - 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
Most 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 (<26), 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.
Use Joda Time. It's recommended by many StackOverflow users and is well documented with examples on timezone conversion.
Good luck!
What's the whole output? Date.toString() should print time zone. Maybe it's not in UTC in your case.