CODEWITHSUNDEEP
javaandroidutc
AndFantasy
AndFantasy

Reputation: 73

Instant.now() returns wrong UTC time ( E.g. 14:24 instead of 02:24 ) +12 hours ahead

So I am trying to get the current UTC time in Java ( I'm using Java 7 with ThreeTenAbp ). I have tried the following calls and all of them return the time in UTC + 12 hours which is not the real UTC time as I have checked online through various source that provide current UTC time.

Instant.now().atZone(ZoneId.of("UTC")).toString();
Instant.now().toString();

Date date = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));

I don't know why these are reporting the wrong UTC time given that I'm explicitly specifying the UTC timezone, except for the second one. I also think it's unlikely that all of these methods of getting the UTC time yield the wrong result so I am wondering what I am doing wrong.

Upvotes: 1

Views: 4889

Answers (2)

pandd
pandd

Reputation: 103

When you print Instant.now().toString(), are you sure the result is not in UTC? Because Instant always works in UTC.

The only thing I can guess is that you're printing the java.util.Date directly, and this class has a terrible toString() method which takes the JVM default timezone.

Maybe if you edit your question and add the inputs and outputs for each case, we can help you better. Because I can't reproduce your problem.

By the way, the current UTC time is (when I tested the code) 2018-03-08T14:47:08.886Z (14:47, or 02:27 PM). If your problem is to print the time in AM/PM format, then you could use a DateTimeFormatter:

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("uuuu-MM-dd'T'hh:mm:ssaX");
String formatted = ZonedDateTime.now(ZoneOffset.UTC).format(fmt);

Using hh gives you the hour in AM/PM (1 to 12), instead of 0 to 23 (which is the default, and also the value returned by HH pattern). I also added a, which gives you AM or PM, to not make the output ambiguous.

Upvotes: 0

Anonymous
Anonymous

Reputation: 86399

While I cannot be sure, of course, the very likely reason for the behaviour you have observed is that you are running your program on a computer or a device the clock of which is set incorrectly. Both Instant.now() and new Date() pick up the time from the system clock, so this would explain nicely.

You may object and ask: How could I set the system clock 12 hours ahead? How could I not discover? While there could be many explanations for this, the two obvious ones are:

  • Setting the system clock 12 hours wrong is not hard, that could easily happen by mistake. If your system is showing the time on a 12 hour clock (digital or analog), it will appear to show the correct time even though the time has been set 12 hours ahead. You will be able to notice that the date is one day ahead every day after 12 noon, though.
  • Your device may have an incorrect time zone setting so that when you set the time to the correct time in your time zone, this really means setting it to the wrong time on the time line. For example: Your device time zone is set to America/Los_Angeles which for a couple of days still is at UTC-8. You are in Dubai, where the current time is UTC+4. At 10 AM in Dubai you set the device time to 10:00, but your device understand it as 10:00 Los Angeles time, which is the equivalent of 22:00 (10 PM) Dubai time. So in this way your clock accidentally gets set 12 hours ahead. And as long as no one correct the time zone setting, it’s hard to detect that anything is wrong. Still it will cause Instant.now() and new Date() to give the incorrect results you observed.

Upvotes: 1

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