Develop Reference

SimpleDateFormat shows wrong local Time

I want to store a string into a databse (SQLite) for an Android App with the current time and date. For that purpose I am using SimpleDateFormat. Unfortunately it does not show the correct time when. I tried two options.
First Option (from SimpleDateFormat with TimeZone)
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z", Locale.getDefault());
sdf.format(new Date());
Second option (from Java SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'") gives timezone as IST)
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss'Z'");
sdf2.setTimeZone(TimeZone.getTimeZone("CEST"));
In both cases the time is just wrong. It is not the local time that my laptop or phone is showing but the output time is 2 hours earlier. How can I change that? I would like to have the current time of Berlin (CEST) that is also shown on my computer. I appreciate every comment.

Use Europe/Berlin instead of CEST and you will get the expected result.
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class Main {
public static void main(String[] args) {
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");
sdf2.setTimeZone(TimeZone.getTimeZone("Europe/Berlin"));
System.out.println(sdf2.format(new Date()));
}
}
Output:
2020-09-27 18:38:04 +0200
A piece of advice:
I recommend you switch from the outdated and error-prone java.util date-time API and SimpleDateFormat to the modern java.time date-time API and the corresponding formatting API (package, java.time.format). Learn more about the modern date-time API from Trail: Date Time. If 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.
Using the modern date-time API:
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
public class Main {
public static void main(String[] args) {
ZonedDateTime zdt = ZonedDateTime.now(ZoneId.of("Europe/Berlin"));
// Default format
System.out.println(zdt);
// Some custom format
System.out.println(zdt.format(DateTimeFormatter.ofPattern("EEEE dd uuuu hh:mm:ss a z")));
}
}
Output:
2020-09-27T18:42:53.620168+02:00[Europe/Berlin]
Sunday 27 2020 06:42:53 pm CEST
The modern API will alert you whereas legacy API may failover:
import java.time.ZoneId;
import java.time.ZonedDateTime;
public class Main {
public static void main(String[] args) {
ZonedDateTime zdt = ZonedDateTime.now(ZoneId.of("CEST"));
// ...
}
}
Output:
Exception in thread "main" java.time.zone.ZoneRulesException: Unknown time-zone ID: CEST
at java.base/java.time.zone.ZoneRulesProvider.getProvider(ZoneRulesProvider.java:279)
at java.base/java.time.zone.ZoneRulesProvider.getRules(ZoneRulesProvider.java:234)
at java.base/java.time.ZoneRegion.ofId(ZoneRegion.java:120)
at java.base/java.time.ZoneId.of(ZoneId.java:408)
at java.base/java.time.ZoneId.of(ZoneId.java:356)
at Main.main(Main.java:6)
As you can see, you get an exception in this case whereas SimpleDateFormat will give you undesirable result as shown below:
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class Main {
public static void main(String[] args) {
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");
sdf2.setTimeZone(TimeZone.getTimeZone("CEST"));
System.out.println(sdf2.format(new Date()));
}
}
Output:
2020-09-27 16:47:45 +0000
You might be wondering what this undesirable result refers to. The answer is: when SimpleDateFormat doesn't understand a time-zone, it failovers (defaults) to GMT (same as UTC) i.e. it has ignored CEST and applied GMT in this case (not a good feature IMHO 😊).

ISO 8601
Assuming that your SQLite hasn’t got a datetime datatype I recommend that you use ISO 8601 format, the international standard, for storing your date-times as strings to SQLite. Next, consider using java.time, the modern Java date and time API, for your date and time work. The two suggestions go nicely hand in hand. Common recommendations say to store date and time in UTC, but I understand that you prefer Europe/Berlin time.
ZoneId databaseTimeZone = ZoneId.of("Europe/Berlin");
ZonedDateTime now = ZonedDateTime.now(databaseTimeZone);
String databaseTime = now.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME);
System.out.println(databaseTime);
Output from the above when running just now:
2020-09-27T15:54:21.53+02:00
I have on purpose included the offset from UTC in the string. This will allow anyone retrieving the string to convert the time to UTC or the time zone of their preference. If the user travels to India to see Taj Mahal and retrieves the data there, converting to India Standard Time is no problem. The offset also disambiguates times in the night in October when Berlin changes from summer time (DST) to standard time and the same clock times repeat. Times before the change will have offset +02:00, times after the change will have +01:00.
How can I change the format(?)
Edit: If you insist on your own format for information and human readability, build a formatter for that. The ZonedDateTime already has the time in your chosen time zone, so that time is also the one you will have when you format it:
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss Z");
String databaseTime = now.format(formatter);
Now the result is:
2020-09-27 16:22:23 +0200
Further edit: Since human readability is the only requirement for that column, go all-in on that and use java’s predefined localized format, for example:
DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG)
.withLocale(Locale.GERMAN);
September 2020 19:06:03 MESZ
If it’s too long for you, use FormatStyle.MEDIUM instead.
Further further edit: And why? The question is whether 27. September 2020 19:06:03 MESZ is easier to read and understand correctly than 2020-09-27 16:22:23 +0200. You should make it as easy for yourself as you reasonably can. There is a point in including the offset, +0200, though, since it is unambiguous whereas a time zone abbreviation like MESZ is not guaranteed to be (many time zone abbreviations are ambiguous).
What went wrong in your code?
You are probably running your code on a computer with its time zone set to UTC (or some other time zone that is currently two hours behind Berlin time). In your second snippet you are trying to make up for this fact by setting the time zone of you formatter to CEST (Central European Summer Time). The way you are doing that is not what you want, and it also does not work. Both have to do with the fact that CEST is not a time zone. CEST is two hours ahead of UTC, and if it had worked, you would have got two hours ahead of UTC also during the standard time of year where Berlin is only 1 hour ahead of UTC, that is, the wrong time. Since CEST is not a time zone, TimeZone does not recognize it as a time zone. And this is as confusing as the TimeZone class is: instead of objecting, it tacitly gives you GMT, so you have got nowhere. I really recommend avoiding using that class. The correct time zone identifier for Berlin is Europe/Berlin, the one I am also using in my code. Time zone identifiers come in the region/city format.
Question: Doesn’t java.time require Android API level 26?
java.time works nicely on both older and newer Android devices. It just requires at least Java 6.
In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
In non-Android Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
On older Android either use desugaring or the Android edition of ThreeTen Backport. It’s called ThreeTenABP. In the latter case make sure you import the date and time classes from org.threeten.bp with subpackages.
Links
Oracle tutorial: Date Time explaining how to use java.time.
Java Specification Request (JSR) 310, where java.time was first described.
ThreeTen Backport project, the backport of java.time to Java 6 and 7 (ThreeTen for JSR-310).
Java 8+ APIs available through desugaring
ThreeTenABP, Android edition of ThreeTen Backport
Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.
Wikipedia article: ISO 8601

Well, i faced the same issue a week ago and I figured out that the problem is in the TimeZone settings
If you are getting the date as a string and you need to format it to another format use the code below
public String getCalendarDate(String inputDate){
Date date = getDateFromSource(inputDate);
SimpleDateFormat formatter = new SimpleDateFormat("EEEE, d MMMM yyyy", Locale.getDefault());
formatter.setTimeZone(TimeZone.getDefault());
return formatter.format(date);
}
Date getDateFromSource(String apiDate){
Date newFormattedDate = null;
SimpleDateFormat parser = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ENGLISH);
parser.setTimeZone(TimeZone.getTimeZone("UTC"));
try {
newFormattedDate = parser.parse(apiDate);
} catch (ParseException e) {
e.printStackTrace();
}
return newFormattedDate;
}
In the getDateFromSource function change the date format to the source format, while in the getCalendarDate function, change the format to your required format.
If you already have the Date object, you can ignore the getDateFromSource function and put it directly in the second one
For those who use Kotlin this is the equivalent code
fun getCalendarDate(apiDate: String): String{
val date = getDateFromApi(apiDate)
val formatter = SimpleDateFormat("EEEE, d MMMM yyyy", Locale.getDefault())
formatter.timeZone = TimeZone.getDefault()
return formatter.format(date)
}
private fun getDateFromApi(apiDate: String) :Date{
val parser = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ENGLISH)
parser.timeZone = TimeZone.getTimeZone("UTC")
return parser.parse(apiDate)!!
}

Date to string parsing [duplicate]

I have the following date: 2011-08-12T20:17:46.384Z. What format is this? I'm trying to parse it with Java 1.4 via DateFormat.getDateInstance().parse(dateStr) and I'm getting
java.text.ParseException: Unparseable date: "2011-08-12T20:17:46.384Z"
I think I should be using SimpleDateFormat for parsing, but I have to know the format string first. All I have for that so far is yyyy-MM-dd, because I don't know what the T means in this string--something time zone-related? This date string is coming from the lcmis:downloadedOn tag shown on Files CMIS download history media type.

The T is just a literal to separate the date from the time, and the Z means "zero hour offset" also known as "Zulu time" (UTC). If your strings always have a "Z" you can use:
SimpleDateFormat format = new SimpleDateFormat(
"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US);
format.setTimeZone(TimeZone.getTimeZone("UTC"));
Or using Joda Time, you can use ISODateTimeFormat.dateTime().

tl;dr
Standard ISO 8601 format is used by your input string.
Instant.parse ( "2011-08-12T20:17:46.384Z" )
ISO 8601
This format is defined by the sensible practical standard, ISO 8601.
The T separates the date portion from the time-of-day portion. The Z on the end means UTC (that is, an offset-from-UTC of zero hours-minutes-seconds). The Z is pronounced “Zulu”.
java.time
The old date-time classes bundled with the earliest versions of Java have proven to be poorly designed, confusing, and troublesome. Avoid them.
Instead, use the java.time framework built into Java 8 and later. The java.time classes supplant both the old date-time classes and the highly successful Joda-Time library.
The java.time classes use ISO 8601 by default when parsing/generating textual representations of date-time values.
The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds. That class can directly parse your input string without bothering to define a formatting pattern.
Instant instant = Instant.parse ( "2011-08-12T20:17:46.384Z" ) ;
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….

Not sure about the Java parsing, but that's ISO8601: http://en.wikipedia.org/wiki/ISO_8601

There are other ways to parse it rather than the first answer. To parse it:
(1) If you want to grab information about date and time, you can parse it to a ZonedDatetime(since Java 8) or Date(old) object:
// ZonedDateTime's default format requires a zone ID(like [Australia/Sydney]) in the end.
// Here, we provide a format which can parse the string correctly.
DateTimeFormatter dtf = DateTimeFormatter.ISO_DATE_TIME;
ZonedDateTime zdt = ZonedDateTime.parse("2011-08-12T20:17:46.384Z", dtf);
or
// 'T' is a literal.
// 'X' is ISO Zone Offset[like +01, -08]; For UTC, it is interpreted as 'Z'(Zero) literal.
String pattern = "yyyy-MM-dd'T'HH:mm:ss.SSSX";
// since no built-in format, we provides pattern directly.
DateFormat df = new SimpleDateFormat(pattern);
Date myDate = df.parse("2011-08-12T20:17:46.384Z");
(2) If you don't care the date and time and just want to treat the information as a moment in nanoseconds, then you can use Instant:
// The ISO format without zone ID is Instant's default.
// There is no need to pass any format.
Instant ins = Instant.parse("2011-08-12T20:17:46.384Z");

java.time
You do not need DateTimeFormatter to parse the given date-time string.
Java SE 8 Date-Time API(java.time API or the modern Date-Time API) is based on ISO 8601 and does not require using a DateTimeFormatter object explicitly as long as the Date-Time string conforms to the ISO 8601 standards.
The Z in the string is the timezone designator for zero-timezone offset. It stands for Zulu and specifies the Etc/UTC timezone (which has the timezone offset of +00:00 hours).
The T in the string is just the Date-Time separator as per the ISO-8601 standards.
Demo:
import java.time.Instant;
import java.time.OffsetDateTime;
import java.time.ZonedDateTime;
public class Main {
public static void main(String[] args) {
String strDateTime = "2011-08-12T20:17:46.384Z";
Instant instant = Instant.parse(strDateTime);
OffsetDateTime odt = OffsetDateTime.parse(strDateTime);
ZonedDateTime zdt = ZonedDateTime.parse(strDateTime);
System.out.println(instant);
System.out.println(odt);
System.out.println(zdt);
}
}
Output:
2011-08-12T20:17:46.384Z
2011-08-12T20:17:46.384Z
2011-08-12T20:17:46.384Z
Learn more about java.time, the modern Date-Time API* from Trail: Date Time.
The legacy Date-time API
The legacy Date-time API (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*.
For the sake of completeness, I've written a solution to parse this Date-Time string using the legacy API.
Do not use 'Z' in the pattern with the Date-Time parsing/formatting API.
As already described above, Z (without quotes) is the timezone designator for zero-timezone offset whereas 'Z' is just a character literal and it does not hold any meaning. Use the format, y-M-d'T'H:m:s.SSSXXX. Check the documentation to learn more about these symbols.
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
public class Main {
public static void main(String[] args) throws ParseException {
String strDateTime = "2011-08-12T20:17:46.384Z";
SimpleDateFormat sdf = new SimpleDateFormat("y-M-d'T'H:m:s.SSSXXX", Locale.ENGLISH);
Date date = sdf.parse(strDateTime);
// ...
}
}
Note that a java.util.Date object is not a real Date-Time object like the modern Date-Time types; rather, it represents the number of milliseconds since the standard base time known as "the epoch", namely January 1, 1970, 00:00:00 GMT (or UTC). Since it does not hold any format and timezone information, it applies the format, EEE MMM dd HH:mm:ss z yyyy and the JVM's timezone to return the value of Date#toString derived from this milliseconds value. If you need to print the Date-Time in a different format and timezone, you will need to use a SimpleDateFormat with the desired format and the applicable timezone e.g.
sdf.setTimeZone(TimeZone.getTimeZone("Etc/UTC"));
String formatted = sdf.format(date);
System.out.println(formatted); // 2011-8-12T20:17:46.384Z
Joda Date-Time API
Quoted below is a notice at 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.
Again, for the sake of completeness, I've written a solution to parse this Date-Time string using the Joda Date-Time API.
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;
public class Main {
public static void main(String[] args) {
String dateTimeStr = "2011-08-12T20:17:46.384Z";
DateTimeFormatter dtf = DateTimeFormat.forPattern("y-M-d'T'H:m:s.SSSZ").withOffsetParsed();
DateTime dateTime = dtf.parseDateTime(dateTimeStr);
System.out.println(dateTime);
}
}
Output:
2011-08-12T20:17:46.384Z
* 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.

If you guys are looking for a solution for Android, you can use the following code to get the epoch seconds from the timestamp string.
public static long timestampToEpochSeconds(String srcTimestamp) {
long epoch = 0;
try {
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
Instant instant = Instant.parse(srcTimestamp);
epoch = instant.getEpochSecond();
} else {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ss.SSSSSS'Z'", Locale.getDefault());
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
Date date = sdf.parse(srcTimestamp);
if (date != null) {
epoch = date.getTime() / 1000;
}
}
} catch (Exception e) {
e.printStackTrace();
}
return epoch;
}
Sample input: 2019-10-15T05:51:31.537979Z
Sample output: 1571128673

In JavaScript
let isoDateTimeString = new Date().toISOString();
Description
Date/time format like "YYYY-MM-DDThh:mm:ss.SSSZ" is ISO 8601 date/time format.

Z represent UTC time zone. With java8+, you can simply use Instant.
public static void main(String[] args) {
String time = "2022-06-08T04:55:01.000Z";
System.out.println(Instant.parse(time).toEpochMilli());
}

You can use the following example.
String date = "2011-08-12T20:17:46.384Z";
String inputPattern = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
String outputPattern = "yyyy-MM-dd HH:mm:ss";
LocalDateTime inputDate = null;
String outputDate = null;
DateTimeFormatter inputFormatter = DateTimeFormatter.ofPattern(inputPattern, Locale.ENGLISH);
DateTimeFormatter outputFormatter = DateTimeFormatter.ofPattern(outputPattern, Locale.ENGLISH);
inputDate = LocalDateTime.parse(date, inputFormatter);
outputDate = outputFormatter.format(inputDate);
System.out.println("inputDate: " + inputDate);
System.out.println("outputDate: " + outputDate);

This technique translates java.util.Date to UTC format (or any other) and back again.
Define a class like so:
import java.util.Date;
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;
public class UtcUtility {
public static DateTimeFormatter UTC = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'").withZoneUTC();
public static Date parse(DateTimeFormatter dateTimeFormatter, String date) {
return dateTimeFormatter.parseDateTime(date).toDate();
}
public static String format(DateTimeFormatter dateTimeFormatter, Date date) {
return format(dateTimeFormatter, date.getTime());
}
private static String format(DateTimeFormatter dateTimeFormatter, long timeInMillis) {
DateTime dateTime = new DateTime(timeInMillis);
String formattedString = dateTimeFormatter.print(dateTime);
return formattedString;
}
}
Then use it like this:
Date date = format(UTC, "2020-04-19T00:30:07.000Z")
or
String date = parse(UTC, new Date())
You can also define other date formats if you require (not just UTC)

#John-Skeet gave me the clue to fix my own issue around this. As a younger programmer this small issue is easy to miss and hard to diagnose. So Im sharing it in the hopes it will help someone.
My issue was that I wanted to parse the following string contraining a time stamp from a JSON I have no influence over and put it in more useful variables. But I kept getting errors.
So given the following (pay attention to the string parameter inside ofPattern();
String str = "20190927T182730.000Z"
LocalDateTime fin;
fin = LocalDateTime.parse( str, DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss.SSSZ") );
Error:
Exception in thread "main" java.time.format.DateTimeParseException: Text
'20190927T182730.000Z' could not be parsed at index 19
The problem? The Z at the end of the Pattern needs to be wrapped in 'Z' just like the 'T' is. Change
"yyyyMMdd'T'HHmmss.SSSZ" to "yyyyMMdd'T'HHmmss.SSS'Z'" and it works.
Removing the Z from the pattern alltogether also led to errors.
Frankly, I'd expect a Java class to have anticipated this.

Facing issue with Calendar object

I have a task in which i need to set hour, minute, meridian programmatically to Calendar object and need to display time in a format hh:mm a. Here below is my code so far.
Calendar calendar = (Calendar)dateNtime.clone();
calendar.set(Calendar.HOUR, 12);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.AM_PM, 1);
SimpleDateFormat dateFormat = new SimpleDateFormat("hh:mm a");
String str = dateFormat.format(calendar.getTimeInMillis());
Where dateNTime is an existing calendar object which i have to use in constructing new one.
All is going fine except only a case while i set 12PM. it always format hh:mm a and results 12:00AM while it should be 12:00PM.
please help if anybody have a good experience with Calendar object and it's known issue or provide me if there is a good tutorial link.

The HOUR field is documented as:
Field number for get and set indicating the hour of the morning or afternoon. HOUR is used for the 12-hour clock (0 - 11).
So instead of setting it to 12, you should set it to 0.
Personally I'd just set the HOUR_OF_DAY field, adding 12 hours if you want to make it PM - and don't set the AM_PM field at all.

java.time
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*.
Solution using java.time, the modern API:
import java.time.LocalTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
public class Main {
public static void main(String[] args) {
// Replace JVM's default timezone, ZoneId.systemDefault() with the applicable
// timezone e.g. ZoneId.of("America/New_York")
ZonedDateTime zdt = ZonedDateTime.now(ZoneId.systemDefault())
.withHour(12)
.withMinute(0);
System.out.println(zdt);
// Get and display just time in default format
LocalTime time = zdt.toLocalTime();
System.out.println(time);
// Display just time in a custom format
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("hh:mm a", Locale.ENGLISH);
// Alternatively, dtf.format(time);
String formatted = dtf.format(zdt);
System.out.println(formatted);
}
}
Output:
2021-06-06T12:00:15.855986+01:00[Europe/London]
12:00:15.855986
12:00 PM
ONLINE DEMO
How to convert Calendar to java.time type?
Instant instant = calendar.toInstant();
// Replace JVM's default timezone, ZoneId.systemDefault() with the applicable
// timezone e.g. ZoneId.of("America/New_York")
ZonedDateTime zdt = instant.atZone(ZoneId.systemDefault());
What if I need Calendar object from java.time type?
For any reason, if you need to convert this object of ZonedDateTime to an object of java.util.Calendar, you can do so as follows:
Calendar calendar = Calendar.getInstance();
calendar.setTime(Date.from(zdt.toInstant()));
Learn more about java.time, the modern Date-Time API* from Trail: Date Time.
Sometimes, comments get deleted and therefore quoting below a valuable comment from Ole V.V.:
For a more accurate conversion to Calendar you may use
GregorianCalendar.from(zdt)
* 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.

How to convert UTC time into local time in Java?

I have time coming from gpslocation service in 1352437114052 format. Can some one tell me how to convert this into local time either in Java or Matlab or Excel.

Create a new Date from your milliseconds since epoch. Then use a DateFormat to format it in your desired timezone.
Date date = new Date(1352437114052L);
DateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
format.setTimeZone(TimeZone.getTimeZone("PST"));
System.out.println(format.format(date));

This is an epoch time and it represents Fri, 09 Nov 2012 04:58:34 GMT. This numeric value is an absolute point in time, irrespective to time zone.
If you want to see that point in time in different time zone, use GregorianCalendar:
Calendar c = new GregorianCalendar(TimeZone.getTimeZone("EST"));
c.setTimeInMillis(1352437114052L);
c.get(Calendar.HOUR_OF_DAY); //20:58 the day before

The modern Java answer using the JVM’s time zone setting (typically the same as your computer’s time zone):
long time = 1_352_437_114_052L;
ZonedDateTime dateTime = Instant.ofEpochMilli(time).atZone(ZoneId.systemDefault());
System.out.println(dateTime);
Running on my computer I get
2012-11-09T05:58:34.052+01:00[Europe/Copenhagen]
To specify a time zone:
ZonedDateTime dateTime = Instant.ofEpochMilli(time).atZone(ZoneId.of("Asia/Almaty"));
2012-11-09T10:58:34.052+06:00[Asia/Almaty]
Question: Will that work on Android too?
To answer tinker’s comment here: Yes. I am using java.time, the modern Java date and time API, and it works nicely on older and newer Android devices. It just requires at least Java 6.
In Java 8 and later and on newer Android devices (from API level 26, I’m told) the modern API comes built-in.
In Java 6 and 7 get the ThreeTen Backport, the backport of the new classes (ThreeTen for JSR 310; see the links at the bottom).
On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.
Links
Oracle tutorial: Date Time explaining how to use java.time.
Java Specification Request (JSR) 310, where java.time was first described.
ThreeTen Backport project, the backport of java.timeto Java 6 and 7 (ThreeTen for JSR-310).
ThreeTenABP, Android edition of ThreeTen Backport
Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.

#Steve Kuo answered the question directly, almost. Here's a more general solution for machine's local time, including daylight saving time, where a is of type BasicFileAttributes as reported from Windows directory entry in public FileVisitResult visitFile(Path f, BasicFileAttributes a) during Files.walkFileTree:
String modifyDate;
Date date = new Date(a.lastModifiedTime().to(TimeUnit.MILLISECONDS));
DateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
format.setTimeZone(TimeZone.getDefault());
modifyDate = (format.format(date)).substring(0,10);

long timeStamp = System.currentTimeMillis();
System.out.println(timeStamp+"");
Calendar calendar = Calendar.getInstance();
calendar.setTimeZone(TimeZone.getDefault());
calendar.setTimeInMillis(timeStamp);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss a z");
String dateString = sdf.format(calendar.getTime());
System.out.println(dateString);
Output :
timestamp : 1528860439258
dateformat from sdf : 2018-06-12 08:27:19 PM PDT

Since new Date(String string) is deprecated now(which is the accepted answer), we can use DateTimeZone.getDefault() to get the system time zone
public String getZonedDate(String dateStr) {
DateTime utcDateTime = new DateTime(dateStr).toDateTime(DateTimeZone.UTC);
return utcDateTime
.toDateTime(DateTimeZone.getDefault()).toString("yyyy-MM-dd'T'HH:mm:ss");
}

What is this date format? 2011-08-12T20:17:46.384Z

I have the following date: 2011-08-12T20:17:46.384Z. What format is this? I'm trying to parse it with Java 1.4 via DateFormat.getDateInstance().parse(dateStr) and I'm getting
java.text.ParseException: Unparseable date: "2011-08-12T20:17:46.384Z"
I think I should be using SimpleDateFormat for parsing, but I have to know the format string first. All I have for that so far is yyyy-MM-dd, because I don't know what the T means in this string--something time zone-related? This date string is coming from the lcmis:downloadedOn tag shown on Files CMIS download history media type.

The T is just a literal to separate the date from the time, and the Z means "zero hour offset" also known as "Zulu time" (UTC). If your strings always have a "Z" you can use:
SimpleDateFormat format = new SimpleDateFormat(
"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US);
format.setTimeZone(TimeZone.getTimeZone("UTC"));
Or using Joda Time, you can use ISODateTimeFormat.dateTime().

tl;dr
Standard ISO 8601 format is used by your input string.
Instant.parse ( "2011-08-12T20:17:46.384Z" )
ISO 8601
This format is defined by the sensible practical standard, ISO 8601.
The T separates the date portion from the time-of-day portion. The Z on the end means UTC (that is, an offset-from-UTC of zero hours-minutes-seconds). The Z is pronounced “Zulu”.
java.time
The old date-time classes bundled with the earliest versions of Java have proven to be poorly designed, confusing, and troublesome. Avoid them.
Instead, use the java.time framework built into Java 8 and later. The java.time classes supplant both the old date-time classes and the highly successful Joda-Time library.
The java.time classes use ISO 8601 by default when parsing/generating textual representations of date-time values.
The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds. That class can directly parse your input string without bothering to define a formatting pattern.
Instant instant = Instant.parse ( "2011-08-12T20:17:46.384Z" ) ;
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….

Not sure about the Java parsing, but that's ISO8601: http://en.wikipedia.org/wiki/ISO_8601

There are other ways to parse it rather than the first answer. To parse it:
(1) If you want to grab information about date and time, you can parse it to a ZonedDatetime(since Java 8) or Date(old) object:
// ZonedDateTime's default format requires a zone ID(like [Australia/Sydney]) in the end.
// Here, we provide a format which can parse the string correctly.
DateTimeFormatter dtf = DateTimeFormatter.ISO_DATE_TIME;
ZonedDateTime zdt = ZonedDateTime.parse("2011-08-12T20:17:46.384Z", dtf);
or
// 'T' is a literal.
// 'X' is ISO Zone Offset[like +01, -08]; For UTC, it is interpreted as 'Z'(Zero) literal.
String pattern = "yyyy-MM-dd'T'HH:mm:ss.SSSX";
// since no built-in format, we provides pattern directly.
DateFormat df = new SimpleDateFormat(pattern);
Date myDate = df.parse("2011-08-12T20:17:46.384Z");
(2) If you don't care the date and time and just want to treat the information as a moment in nanoseconds, then you can use Instant:
// The ISO format without zone ID is Instant's default.
// There is no need to pass any format.
Instant ins = Instant.parse("2011-08-12T20:17:46.384Z");

java.time
You do not need DateTimeFormatter to parse the given date-time string.
Java SE 8 Date-Time API(java.time API or the modern Date-Time API) is based on ISO 8601 and does not require using a DateTimeFormatter object explicitly as long as the Date-Time string conforms to the ISO 8601 standards.
The Z in the string is the timezone designator for zero-timezone offset. It stands for Zulu and specifies the Etc/UTC timezone (which has the timezone offset of +00:00 hours).
The T in the string is just the Date-Time separator as per the ISO-8601 standards.
Demo:
import java.time.Instant;
import java.time.OffsetDateTime;
import java.time.ZonedDateTime;
public class Main {
public static void main(String[] args) {
String strDateTime = "2011-08-12T20:17:46.384Z";
Instant instant = Instant.parse(strDateTime);
OffsetDateTime odt = OffsetDateTime.parse(strDateTime);
ZonedDateTime zdt = ZonedDateTime.parse(strDateTime);
System.out.println(instant);
System.out.println(odt);
System.out.println(zdt);
}
}
Output:
2011-08-12T20:17:46.384Z
2011-08-12T20:17:46.384Z
2011-08-12T20:17:46.384Z
Learn more about java.time, the modern Date-Time API* from Trail: Date Time.
The legacy Date-time API
The legacy Date-time API (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*.
For the sake of completeness, I've written a solution to parse this Date-Time string using the legacy API.
Do not use 'Z' in the pattern with the Date-Time parsing/formatting API.
As already described above, Z (without quotes) is the timezone designator for zero-timezone offset whereas 'Z' is just a character literal and it does not hold any meaning. Use the format, y-M-d'T'H:m:s.SSSXXX. Check the documentation to learn more about these symbols.
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
public class Main {
public static void main(String[] args) throws ParseException {
String strDateTime = "2011-08-12T20:17:46.384Z";
SimpleDateFormat sdf = new SimpleDateFormat("y-M-d'T'H:m:s.SSSXXX", Locale.ENGLISH);
Date date = sdf.parse(strDateTime);
// ...
}
}
Note that a java.util.Date object is not a real Date-Time object like the modern Date-Time types; rather, it represents the number of milliseconds since the standard base time known as "the epoch", namely January 1, 1970, 00:00:00 GMT (or UTC). Since it does not hold any format and timezone information, it applies the format, EEE MMM dd HH:mm:ss z yyyy and the JVM's timezone to return the value of Date#toString derived from this milliseconds value. If you need to print the Date-Time in a different format and timezone, you will need to use a SimpleDateFormat with the desired format and the applicable timezone e.g.
sdf.setTimeZone(TimeZone.getTimeZone("Etc/UTC"));
String formatted = sdf.format(date);
System.out.println(formatted); // 2011-8-12T20:17:46.384Z
Joda Date-Time API
Quoted below is a notice at 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.
Again, for the sake of completeness, I've written a solution to parse this Date-Time string using the Joda Date-Time API.
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;
public class Main {
public static void main(String[] args) {
String dateTimeStr = "2011-08-12T20:17:46.384Z";
DateTimeFormatter dtf = DateTimeFormat.forPattern("y-M-d'T'H:m:s.SSSZ").withOffsetParsed();
DateTime dateTime = dtf.parseDateTime(dateTimeStr);
System.out.println(dateTime);
}
}
Output:
2011-08-12T20:17:46.384Z
* 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.

If you guys are looking for a solution for Android, you can use the following code to get the epoch seconds from the timestamp string.
public static long timestampToEpochSeconds(String srcTimestamp) {
long epoch = 0;
try {
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
Instant instant = Instant.parse(srcTimestamp);
epoch = instant.getEpochSecond();
} else {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ss.SSSSSS'Z'", Locale.getDefault());
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
Date date = sdf.parse(srcTimestamp);
if (date != null) {
epoch = date.getTime() / 1000;
}
}
} catch (Exception e) {
e.printStackTrace();
}
return epoch;
}
Sample input: 2019-10-15T05:51:31.537979Z
Sample output: 1571128673

In JavaScript
let isoDateTimeString = new Date().toISOString();
Description
Date/time format like "YYYY-MM-DDThh:mm:ss.SSSZ" is ISO 8601 date/time format.

Z represent UTC time zone. With java8+, you can simply use Instant.
public static void main(String[] args) {
String time = "2022-06-08T04:55:01.000Z";
System.out.println(Instant.parse(time).toEpochMilli());
}

You can use the following example.
String date = "2011-08-12T20:17:46.384Z";
String inputPattern = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
String outputPattern = "yyyy-MM-dd HH:mm:ss";
LocalDateTime inputDate = null;
String outputDate = null;
DateTimeFormatter inputFormatter = DateTimeFormatter.ofPattern(inputPattern, Locale.ENGLISH);
DateTimeFormatter outputFormatter = DateTimeFormatter.ofPattern(outputPattern, Locale.ENGLISH);
inputDate = LocalDateTime.parse(date, inputFormatter);
outputDate = outputFormatter.format(inputDate);
System.out.println("inputDate: " + inputDate);
System.out.println("outputDate: " + outputDate);

This technique translates java.util.Date to UTC format (or any other) and back again.
Define a class like so:
import java.util.Date;
import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;
public class UtcUtility {
public static DateTimeFormatter UTC = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'").withZoneUTC();
public static Date parse(DateTimeFormatter dateTimeFormatter, String date) {
return dateTimeFormatter.parseDateTime(date).toDate();
}
public static String format(DateTimeFormatter dateTimeFormatter, Date date) {
return format(dateTimeFormatter, date.getTime());
}
private static String format(DateTimeFormatter dateTimeFormatter, long timeInMillis) {
DateTime dateTime = new DateTime(timeInMillis);
String formattedString = dateTimeFormatter.print(dateTime);
return formattedString;
}
}
Then use it like this:
Date date = format(UTC, "2020-04-19T00:30:07.000Z")
or
String date = parse(UTC, new Date())
You can also define other date formats if you require (not just UTC)

#John-Skeet gave me the clue to fix my own issue around this. As a younger programmer this small issue is easy to miss and hard to diagnose. So Im sharing it in the hopes it will help someone.
My issue was that I wanted to parse the following string contraining a time stamp from a JSON I have no influence over and put it in more useful variables. But I kept getting errors.
So given the following (pay attention to the string parameter inside ofPattern();
String str = "20190927T182730.000Z"
LocalDateTime fin;
fin = LocalDateTime.parse( str, DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss.SSSZ") );
Error:
Exception in thread "main" java.time.format.DateTimeParseException: Text
'20190927T182730.000Z' could not be parsed at index 19
The problem? The Z at the end of the Pattern needs to be wrapped in 'Z' just like the 'T' is. Change
"yyyyMMdd'T'HHmmss.SSSZ" to "yyyyMMdd'T'HHmmss.SSS'Z'" and it works.
Removing the Z from the pattern alltogether also led to errors.
Frankly, I'd expect a Java class to have anticipated this.