Develop Reference

Joda DateTime Timezone doesn't show up correctly

I'm using Joda-Time DateTime in Android.
It seems that the DateTimeZone doesn't work correctly. Maybe it has something to do with daylight savings?
At this moment, we have GMT +2. This will change in a few weeks, for the winter. Then it will be GMT +1. But right now it's not correct.
import org.joda.time.DateTime
import org.joda.time.DateTimeZone
import org.joda.time.LocalDateTime
// GMT: Thursday 26 October 2017 12:11:54
val epochTime: Long = 1509019914
var dateServer = LocalDateTime(epochTime * 1000).toDateTime(DateTimeZone.forID("Europe/Amsterdam"))
Expected (correct time in Amsterdam):
14:11:54 GMT+02:00 DST
Actual:
13:11 2017-10-26T13:11:54.000+01:00

The LocalDateTime constructor gets the epochTime value and converts to the default timezone to get the date and time values - check the value of DateTimeZone.getDefault(), it's probably a timezone that's currently using the +01:00 offset.
Then the toDateTime method creates a DateTime that corresponds to the same date and time represented by the LocalDateTime, but at the specified timezone (it just "attaches" the timezone to the date/time values, and no conversion is made).
If you want to get the date and time that corresponds to the epochTime in a specific timezone, just create the DateTime directly:
val dateServer = DateTime(epochTime * 1000, DateTimeZone.forID("Europe/Amsterdam"));
With this, dateServer will be:
2017-10-26T14:11:54.000+02:00
An example in my default timezone, just to be more clear. My default timezone (returned by DateTimeZone.getDefault()) is America/Sao_Paulo, which is using the offset -02:00 (2 hours behind UTC) at October 26th 2017.
The epochTime 1509019914 corresponds to UTC 2017-10-26T12:11:54Z.
When I do LocalDateTime(epochTime * 1000), it gets the corresponding UTC value (12:11) and converts to the default timezone: in my case, to 10:11, so the LocalDateTime will have the value 2017-10-26T10:11:54.
Then the toDateTime method just creates a DateTime that corresponds to the same date and time (2017-10-26T10:11:54), at the specified timezone. So it creates 2017-10-26T10:11:54 at Amsterdam (+02:00).
Your default timezone is probably one that uses the +01:00 offset, which would explain the difference you're getting (12:11 UTC is first converted to LocalDateTime with 13:11, and then toDateTime creates 13:11 at Amsterdam).
JSR310 - new date/time API
Joda-Time is in maintainance mode and is being replaced by the new APIs, so I don't recommend start a new project with it. Even in joda's website it says: "Note that Joda-Time is considered to be a largely “finished” project. No major enhancements are planned. If using Java SE 8, please migrate to java.time (JSR-310).".
If you can't (or don't want to) migrate from Joda-Time to the new API, you can ignore this section.
In Android, you can use the ThreeTen Backport, a great backport for Java 8's new date/time classes. To make it work, you'll also need the ThreeTenABP (more on how to use it here).
To get the corresponding UTC instant from the epochTime, you can use the org.threeten.bp.Instant class. Then you use a org.threeten.bp.ZoneId to convert it to a timezone, resulting in a org.threeten.bp.ZonedDateTime:
val dateServer = Instant.ofEpochSecond(epochTime).atZone(ZoneId.of("Europe/Amsterdam"));
dateServer will be a org.threeten.bp.ZonedDateTime, with the value corresponding to 2017-10-26T14:11:54+02:00[Europe/Amsterdam].

Why is JodaTime timezone shifting a date time?

When the string "2017-04-21T17:46:00Z" is passed into the first method the resulting formatted date string is "06:46 21 Apr 2017". Why is the hour moving by eleven hours? The input strings are being provided by an HTTP server application in JSON. I thought the Z suffix referred to Zulu, ie GMT.
private static final String DATE_TIME_FORMAT = "hh:mm dd MMM yyyy";
public static String formatTimestamp(String dateTimestamp) {
DateTime dateTime = getDateTimeFromTimestamp(dateTimestamp);
DateTimeFormatter fmt = DateTimeFormat.forPattern(DATE_TIME_FORMAT);
return fmt.print(dateTime);
}
private static DateTime getDateTimeFromTimestamp(String dateTimestamp) {
return new DateTime(dateTimestamp);
}
I suspect it relates to timezones but it's not clear how or where. The code is running on an Android device in the UK, in the GMT timezone.

I've made a test with java 7 and joda-time 2.7 (but not the Android's version)
That's how I could reproduce the problem:
// changing my default timezone (because I'm not in UK)
DateTimeZone.setDefault(DateTimeZone.forID("Europe/London"));
// calling your method
System.out.println(formatTimestamp("2017-04-21T17:46:00Z"));
The output is
06:46 21 Abr 2017
To check what's wrong, I've changed the date format to:
DATE_TIME_FORMAT2 = "hh:mm a dd MMM yyyy Z z zzzz";
Where a means "AM or PM", Z is the timezone offset/id, z is the timezone "short" name and zzzz is the timezone "long" name. Using this format, the output is:
06:46 PM 21 Abr 2017 +0100 BST British Summer Time
So the datetime created is 6PM, just one hour ahead of input, not eleven hours as you thought (actually if you change the format to HH instead of hh, the hours will be 18 instead of 06).
Also note the timezone fields: +0100 BST British Summer Time. The first part (+0100) means that this DateTime is one hour ahead of GMT, and BST British Summer Time means it's in British's Daylight Saving Time.
So, to have your output equals to your input, you have 2 alternatives:
1. Change your default timezone to UTC:
DateTimeZone.setDefault(DateTimeZone.UTC);
System.out.println(formatTimestamp("2017-04-21T17:46:00Z"));
The output will be:
05:46 21 Apr 2017
If you want to change the hours to be 17:46, change your date format, replacing hh by HH
2. Use the DateTime constructor that receives a DateTimeZone:
private static DateTime getDateTimeFromTimestamp(String dateTimestamp) {
// creates a DateTime in UTC
return new DateTime(dateTimestamp, DateTimeZone.UTC);
}
The output will be the same as alternative 1, but in this case you don't need to change the default timezone.
For me, alternative 2 makes more sense, because:
you don't need to change the default timezone (which can cause some mess in other parts of the application)
you already know that all dates handled by this code are in UTC time (because of the "Z" in the end)

Using java.time
The Answer by Hugo seems to be correct and informative. But FYI, the Joda-Time project is now in maintenance mode, with the team advising migration to the java.time classes. For Android, see the last bullet at bottom below.
Your input string is in standard ISO 8601 format. The java.time classes use standard formats when parsing & generating strings. So no need to specify a formatting pattern.
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).
String input = "2017-04-21T17:46:00Z" ;
Instant instant = Instant.parse( input ) ;
instant.toString(): 2017-04-21T17:46:00Z
For more flexible formatting such as you desire, convert to an OffsetDateTime object were you can specify any offset-from-UTC in hours and minutes. We want UTC itself (an offset of zero) so we can use the constant ZoneOffset.UTC.
OffsetDateTime odt = instant.atOffset( ZoneOffset.UTC ) ;
odt.toString(): 2017-04-21T17:46Z
Define a formatting pattern to match your desired format. Note that you must specify a 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.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "hh:mm dd MMM yyyy" , Locale.US ) ;
String output = odt.format( f ) ;
output: 05:46 21 Apr 2017
If you want to see this same moment through the lens of a region’s wall-clock time such as Europe/London or Pacific/Auckland, apply a time zone to get a ZonedDateTime.
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 or BST as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "Europe/London" ) ;
ZonedDateTime zdt = instant.atZone( z ) ;
Note the time-of-day is an hour off because of Daylight Saving Time (DST).
zdt.toString(): 2017-04-21T18:46+01:00[Europe/London]
See this code run live at IdeOne.com.
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.
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
The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
See How to use ThreeTenABP….

Converting milliseconds to Date object

I am having following code to convert milliseconds to Android Date object.
Date dateObj = new Date(milli);
But problem is that my milliseconds value is having GMT value added in it before i pass it to Date class, add when i print this date object i can see that date object is again adding GMT value in the milliseconds value and because of that my date is displayed as wrong.
So how can i generate Date object with out considering GMT value in it.
For example my milliseconds are 1385569800000 which is getting printed as below:
Wed, 27 Nov 2013 22:00:00 --> +5.30
But the current value of this time stamp without adding GMT is:
Wed, 27 Nov 2013 16:30:00
*UPDAE*
It is not just about printing the date in right format and with right date time.
But i want to use that date object to schedule TimeTask.
So basically i want to create Date object which has proper date time value in it with out adding extra GMT time added in it.

A Date is always in UTC. No need to change that.
When printing the date value, use SimpleDateFormat and call setTimeZone() on it before formatting the output string.
It is not just about printing the date in right format and with right date time.
But i want to use that date object to schedule TimeTask.
TimerTask is just a task and not its scheduling. Timer accepts a Date object for scheduling. The Date is in UTC there as well.

try my code if you a
long currentTime = System.currentTimeMillis();
TimeZone tz = TimeZone.getDefault();
Calendar cal = GregorianCalendar.getInstance(tz);
int offsetInMillis = tz.getOffset(cal.getTimeInMillis());
currentTime -= offsetInMillis;
Date date = new Date(currentTime);
it is work for me

You can try with joda-time API.
Joda-Time provides a quality replacement for the Java date and time classes. The design allows for multiple calendar systems, while still providing a simple API. The 'default' calendar is the ISO8601 standard which is used by XML. The Gregorian, Julian, Buddhist, Coptic, Ethiopic and Islamic systems are also included, and we welcome further additions. Supporting classes include time zone, duration, format and parsing.
http://joda-time.sourceforge.net/key_instant.html

A Date object simply represents a moment in time. Imagine you're on the phone to someone on a different continent, and you say "3...2...1...NOW!". That "NOW" is the same moment for both of you, even though for one person it's 9am and for the other it's 4pm.
You're creating a Date representing the moment 1385569800000 milliseconds after the Java epoch (the beginning of 1970, GMT). That is your "NOW", and it's fixed and unchanging. What it looks like converted into text, however, depends on which timezone you want to display it for. Java defaults to using GMT, which would be right if you were in Britain during the winter, but for (I'm guessing) India you want it in a different time zone. Laalto's answer shows you how to do that.

here is the code,that worked like charm for me:
public static String getDate(long milliSeconds, String dateFormat)
{
// Create a DateFormatter object for displaying date in specified format.
DateFormat formatter = new SimpleDateFormat(dateFormat);
// Create a calendar object that will convert the date and time value in milliseconds to date.
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(milliSeconds);
return formatter.format(calendar.getTime());
}

How to calculate the difference of hours between two current times based on location

I know this may be a simple/duplicate question but somehow I can't manage to calculate it
Hello, I am fetching today's twitter feeds with their tweeting times and have to calculate the difference of hours between them based on location to show. This is a sample date Sun Jul 21 21:14:40 +0000 2013 and I need to calculate the difference of hours with current time.

So, the first thing to do is to parse that string into a date:
Date postDate = new java.text.SimpleDateFormat("E MMM d HH:mm:ss Z yyyy")
.parse("Sun Jul 21 21:14:40 +0000 2013");
Now, you can get the difference between the post date and the current date in milliseconds:
long diffMSec = new Date().getTime() - postDate.getTime();
Finally, you can convert the milliseconds to hours, or any other time unit:
int diffHours = diffMSec / (1000*60*60);
Note that dates only have time zones when represented as strings - internally they're stored as milliseconds since midnight, Jan. 1, 1980, UTC. So parsing the string to a date (using a time zone), and calculating the diff between two dates takes care of the timezone difference for you.

joda-time can't read Parse dateTime string

I'm having an issue with joda-time formatting a date time string that Parse (parse.com) has stored in an sqlite table.
Sqlite creation string: "createdDate date time"
Storing parse date into table: "insert... parseObject.getCreatedAt()"
If i then use a SQLite browser to inspect the table, I see the date stored like this:
Sat Jun 15 15:44:52 PDT 2013
So going along with that, I wrote the following to convert it back into a DateTime object to give to parse as part of a query to get items that are newer than the last inserted in my table:
DateTimeFormatter format = DatetimeFormat.forPattern("yyyy'-'MM'-'dd'T'HH':'mm':'ss.SSS'Z'");
DateTime dt = formatter.parseDateTime(datahelper.getLastInsertDate(..));
The formatter is this way, because in Parse's databrowser, I can see dateTimes being stored like this:
2013-06-24T08:11:45.280Z
I get an ANR though, so I tried using the following formatter:
DateTimeFormatter format = DatetimeFormat.forPattern("EEE' 'MMM' 'dd' 'HH':'mm':'ss 'z'' 'YYYY");
DateTime dt = formatter.parseDateTime(datahelper.getLastInsertDate(..));
and I still get an ANR. The trace in eclipse shows the following:
Caused by: java.lang.IllegalArgumentException: invalid format: "Tue Jun 25 00:13:29 PDT 2013"
at org.joda.time.format.DateTimeFormatter.parseDateTime"
The second ANR trace shows:
Invalid format: "Tue Jun 25 00:13:29 PDT 2013" is malformed at "PDT
2013"
I've tried getting around that, as joda time does not parse "z" to PDT/PST, so I've put 'PDT' in my formatter to hopefully get it to work, but nothing seems to work.
Any ideas?
Edit 1: Using the accepted answer, I have a timezone formatting issue)
DateFormat originalFormat = new SimpleDateFormat("EEE MMM DDD HH:mm:ss z yyyy");
Date originaldate = originalFormat.parse(datahelper.getLastInsertdate);
Log.i("converted date: ", String.valueOf(originalDate);
Log.i("a real date: ", "String.valueOf(new Date(new Date().getTime)));
I get two outputs:
Fri Jan 25 15:14:11 PST 2013
Tue Jun 25 17:11:44 PDT 2013
why does the converted date show PST, and a standard Date shows PDT?

It seems to be a known problem Joda cannot parse Timezone names sadly. In the documentation before all the pattern syntaxes you will see this line:
The pattern syntax is mostly compatible with java.text.SimpleDateFormat - time zone names cannot be parsed and a few more symbols are supported. All ASCII letters are reserved as pattern letters, which are defined as follows:
You can see that in the documentation link here
Now the solution to your answer can be found in this answer by #BalusC located here
Hope this helps.

I think that with SQLite, because the date type is somewhat broken, the best thing to do is to store the long that you get from Date.getTime() or related Joda methods.
When you get the long from the database, re-construct your date object (e.g. new Date(long)), and then format that.
Above all, remember that (IMHO) the only sensible way to store a date is in reference to UTC, which is what you get with Date.getTime() and new Date(long) : milliseconds since Jan 1, 1970 UTC.
Once you retrieve your date, format it with whatever timezone is appropriate.