DateFormat parse - not return date in UTC
Excuse me for mentioning it, I suspect that there is no problem in your code, there’s only confusion. If you think the old Date
class is behaving confusingly, allow me to be the first of many to agree with you. The good and sound solution to this problem is you stop using Date
and start using the modern Java date and time API instead.
Since you are coding for Android, you first step is to get the ThreeTenABP, the library for Android that offers the modern API (if you were using Java 8 or 9, you could skip this step since the modern API wold be built in). The details are described in this question: How to use ThreeTenABP in Android Project. Now you can do:
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss Z");
String dateUTCAsString = "2017-11-15T12:54:25 +0000";
Instant dateResult = OffsetDateTime.parse(dateUTCAsString, formatter).toInstant();
System.out.println(dateResult);
On my computer this just printed:
2017-11-15T12:54:25Z
The Z
at the end means Zulu time zone or UTC.
As you may know, System.out.println(dateResult)
implicitly calls the toString
method of the dateResult
object. Objects of the class Instant
produce the above format, always in UTC, as I understood you wanted. The Instant
class is the natural replacement for the old-fashioned Date
class for most purposes. Internally the Instant
holds the number of seconds and nanoseconds since the epoch, which is defined as January 1 1970 at 0:00 midnight UTC. I encourage you to consider this an irrelevant implementation detail. An Instant
is a point on the time-line.
What went wrong?
You asked for a date in UTC. Depending on how you look at it, you can or cannot have this.
- On one hand a
Date
is implemented as the number of seconds and milliseconds since the epoch, so if you use the above definition of the epoch, you may say that it is always in UTC. - On the other hand you shouldn’t worry about implementation details. Conceptually a
Date
(like anInstant
) is a point on the time-line, and does not and cannot have a time zone or offset; it cannot be in UTC. To make matters more confusing, when you do"getCurrentDateUTC: dateResult = " + dateResult
, thendateResult.toString()
is implicitly called. This method grabs your JVM’s time zone setting and converts the date-time to this zone and uses it for the generated string (without modifying theDate
object). This is why you will see the time in EET on your computer or device no matter whichDate
you try to print.
java.time
or JSR-310
The modern date and time API is know as java.time
or JSR-310. One good source for learning to use it is the Oracle tutorial.