问题
I have seconds since 1970 january 1 UTC (Epoch time).
1320105600
I need to convert that seconds into date and time in below format.
Friday,November 4,2011 5:00,AM
How can I achieve this?
回答1:
In case you're restricted to legacy java.util.Date and java.util.Calendar APIs, you need to take into account that the timestamps are interpreted in milliseconds, not seconds. So you first need to multiply it by 1000 to get the timestamp in milliseconds.
long seconds = 1320105600;
long millis = seconds * 1000;
This way you can feed it to a.o. the constructor of java.util.Date and finally use SimpleDateFormat to convert a java.util.Date to java.lang.String in the desired date format pattern, if necessary with a predefined time zone (otherwise it would use the system default time zone, which is not GMT/UTC per se and thus the formatted time might be off).
Date date = new Date(millis);
SimpleDateFormat sdf = new SimpleDateFormat("EEEE,MMMM d,yyyy h:mm,a", Locale.ENGLISH);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
String formattedDate = sdf.format(date);
System.out.println(formattedDate); // Tuesday,November 1,2011 12:00,AM
In case you're already on Java8, there's a LocalDateTime#ofEpochSecond() which allows you to feed epoch seconds directly without the need for multiplying into milliseconds flavor.
LocalDateTime dateTime = LocalDateTime.ofEpochSecond(seconds, 0, ZoneOffset.UTC);
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("EEEE,MMMM d,yyyy h:mm,a", Locale.ENGLISH);
String formattedDate = dateTime.format(formatter);
System.out.println(formattedDate); // Tuesday,November 1,2011 12:00,AM
回答2:
long yourSeconds = 1320105600L;
Date d = new Date(yourSeconds * 1000);
See this javadoc for more info. The constructor needs milliseconds.
To display this date in an appropriate format you should check DateFormat
Here is an example:
DateFormat df = new SimpleDateFormat("dd MMM yyyy hh:mm:ss zzz");
System.out.println(df.format(date));
回答3:
java.time
The Answer by BalusC is good in that it points you to using java.time. But that Answer uses LocalDateTime where Instant is more appropriate. A LocalDateTime is not a moment on the timeline as it purposely has no concept of offset-from-UTC or time zone.
java.time
The java.time framework is built into Java 8 and later. These classes supplant the old troublesome date-time classes such as java.util.Date, .Calendar, & java.text.SimpleDateFormat. The Joda-Time team also advises migration to java.time.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations.
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport and further adapted to Android in ThreeTenABP.
Instant
A moment on the timeline in UTC with a resolution up to nanoseconds is represented by the Instant class.
Instant instant = Instant.ofEpochSecond ( 1_320_105_600L );
Dump to console. Your input value is the first moment of November 1, 2011 in UTC. The Z on the end, short for 'Zulu', means UTC.
System.out.println ( "instant: " + instant );
instant: 2011-11-01T00:00:00Z
ZonedDateTime
In your comments you mention wanting to see this date-time through the lens of the America/Chicago time zone. Use a proper time zone name. Apply a time zone, ZoneId, to get a ZonedDateTime object. We see that Chicago is five hours behind UTC on that date.
ZoneId zoneId = ZoneId.of ( "America/Chicago" );
ZonedDateTime zdt = instant.atZone ( zoneId );
zdt: 2011-10-31T19:00-05:00[America/Chicago]
Strings
The Strings seen above are in standard ISO 8601 format. To generate strings in other formats, use the DateTimeFormatter class. You can specify your own custom pattern. But generally best to let java.time automatically localize to the human language and cultural norms encoded in a Locale object.
DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDateTime ( FormatStyle.FULL );
formatter = formatter.withLocale ( Locale.US );
String output = zdt.format ( formatter );
Monday, October 31, 2011 7:00:00 PM CDT
To specify your own custom format, search Stack Overflow for many examples and more discussion.
回答4:
int seconds = 1320105600;
Date date = new Date(seconds * 1000);
SimpleDateFormat sdf = new SimpleDateFormat("EEEE,MMMM d,yyyy h:mm,a");
System.out.println(sdf.format(date));
回答5:
The trick is to use java.util.Date and java.text.DateFormat to get the format you want. You can look up how to do it in tutorials on the Web.
来源：https://stackoverflow.com/questions/8262333/convert-epoch-seconds-to-date-and-time-format-in-java