Changing Java Timestamp format causes a change of the timestamp

Question

I\'m a bit puzzled regarding the Java timestamp formatting functions as they seem to change the timestamp by a few minutes.

My Pivotal CloudFoundry app writes a new

Answer 1

First, I was really puzzled and thought, you might have found some kind of bug in SimpleDateFormat. Your code can be reduced to the following lines to show the same behaviour:

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSSS");
String str = "2018-06-18 13:07:27.624828+02";
System.out.println(str);
System.out.println(format.parse(str));

Result:

2018-06-18 13:07:27.624828+02
Mon Jun 18 13:17:51 CEST 2018

The parsed Date object got ten additional minutes (and some seconds).

Taking a closer look reveals the problem - it is NOT a bug in JDK:

Your millisecond-part is 624828 - these are six(!) digits (not three). 624828 milliseconds are about 624 seconds, which are 10 minutes and 24 seconds. The SimpleDateFormat correctly summed up this additional seconds and minutes.

What's wrong too: Your date format contains five digits for the milliseconds part.

Solution:

The (new) Java Time API can handle larger fractions of a second - and also convert easily between different time zones:

String str = "2018-06-18 13:07:27.624828+02";
DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSSSSx");
OffsetDateTime date = OffsetDateTime.parse(str, pattern);
System.out.println(date);
System.out.println(date.withOffsetSameInstant(ZoneOffset.UTC));

Result:

2018-06-18T13:07:27.624828+02:00
2018-06-18T11:07:27.624828Z

Answer 2

Your input date contains micro seconds but SimpleDateFormat supports only milli seconds (up to 3 digits). When parsing the value with the flag lenient enabled the complete 6 digits are evaluated as micro seconds. So at the end you have 624 seconds that are added to the date additionally.

You can try to use the SSSSSS pattern with DateTimeFormatter that has been introduced in Java 8.

But you may have further issues. Your code parses the input date without the time zone information +02 that is included at the end. You should add one letter X for the ISO8601 time zone format. When formatting the date for outputting you use letter 'Z' that indicates time zone UTC. But you set time zone CET (Berlin). So the output date is not in UTC. The correct ouput in UTC for the specified input date is:

2018-06-18 11:07:27Z