How to convert currentTimeMillis to a date in Java

Question

I have milliseconds in certain log file generated in server, I also know the locale from where the log file was generated, my problem is to convert milliseconds to date in specified format. The processing of that log is happening on server located in different time zone. While converting to "SimpleDateFormat" program is taking date of the machine as such formatted date do not represent correct time of the server. Is there any way to handle this elegantly ?

long yourmilliseconds = 1322018752992l;
        //1322018752992-Nov 22, 2011 9:25:52 PM 

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss,SSS",Locale.US);

GregorianCalendar calendar = new GregorianCalendar(TimeZone.getTimeZone("US/Central"));
calendar.setTimeInMillis(yourmilliseconds);

System.out.println("GregorianCalendar -"+sdf.format(calendar.getTime()));

DateTime jodaTime = new DateTime(yourmilliseconds, 
                    DateTimeZone.forTimeZone(TimeZone.getTimeZone("US/Central")));
DateTimeFormatter parser1 = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss,SSS");

System.out.println("jodaTime "+parser1.print(jodaTime));

Output:

Gregorian Calendar -2011-11-23 08:55:52,992
jodaTime 2011-11-22 21:25:52,992

Answer 1

Easiest way:

private String millisToDate(long millis){

    return DateFormat.getDateInstance(DateFormat.SHORT).format(millis);
    //You can use DateFormat.LONG instead of SHORT

}

Answer 2

You may use java.util.Date class and then use SimpleDateFormat to format the Date.

Date date=new Date(millis);

We can use java.time package (tutorial) - DateTime APIs introduced in the Java SE 8.

var instance = java.time.Instant.ofEpochMilli(millis);
var localDateTime = java.time.LocalDateTime
                        .ofInstant(instance, java.time.ZoneId.of("Asia/Kolkata"));
var zonedDateTime = java.time.ZonedDateTime
                            .ofInstant(instance,java.time.ZoneId.of("Asia/Kolkata"));

// Format the date

var formatter = java.time.format.DateTimeFormatter.ofPattern("u-M-d hh:mm:ss a O");
var string = zonedDateTime.format(formatter);

Answer 3

tl;dr

Instant.ofEpochMilli( 1_322_018_752_992L )     // Parse count of milliseconds-since-start-of-1970-UTC into an `Instant`.
       .atZone( ZoneId.of( "Africa/Tunis" ) )  // Assign a time zone to the `Instant` to produce a `ZonedDateTime` object.

Details

The other answers use outmoded or incorrect classes.

Avoid the old date-time classes such as java.util.Date/.Calendar. They have proven to be poorly designed, confusing, and troublesome.

java.time

The java.time framework comes built into Java 8 and later. Much of the functionality is backported to Java 6 & 7 and further adapted to Android. Made by the some of the same folks as had made Joda-Time.

An Instant is a moment on the timeline in UTC with a resolution of nanoseconds. Its epoch is first moment of 1970 in UTC.

Assuming your input data is a count of milliseconds from 1970-01-01T00:00:00Z (not clear in the Question), then we can easily instantiate an Instant.

Instant instant = Instant.ofEpochMilli( 1_322_018_752_992L );

instant.toString(): 2011-11-23T03:25:52.992Z

The Z in that standard ISO 8601 formatted string is short for Zulu and means UTC.

Apply a time zone using a proper time zone name, to get a ZonedDateTime.

ZoneId zoneId = ZoneId.of( "Asia/Kolkata" ) ;
ZonedDateTime zdt = instant.atZone( zoneId );

See this code run live at IdeOne.com.

Asia/Kolkata time zone ?

I am guessing your are had an India time zone affecting your code. We see here that adjusting into Asia/Kolkata time zone renders the same time-of-day as you report, 08:55 which is five and a half hours ahead of our UTC value 03:25.

2011-11-23T08:55:52.992+05:30[Asia/Kolkata]

Default zone

You can apply the current default time zone of the JVM. Beware that the default can change at any moment during runtime. Any code in any thread of any app within the JVM can change the current default. If important, ask the user for their desired/expected time zone.

ZoneId zoneId = ZoneId.systemDefault();
ZonedDateTime zdt = ZonedDateTime.ofInstant( instant , zoneId );

---

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.

Answer 4

The easiest way to do this is to use the Joda DateTime class and specify both the timestamp in milliseconds and the DateTimeZone you want.

I strongly recommend avoiding the built-in Java Date and Calendar classes; they're terrible.