How to use ZoneOffset, ZoneId with LocalDateTime properly in Java 8?

Question

The objective here is to convert LocalDateTime to epoch second back and forth.

Suppose I have a LocalDateTime defined as:

LocalDateTime now = LocalDateTime.now();

I want to convert it to epoch second in time Asia/Kolkata time zone which I can do like:

long epochSecondNow = now.atZone(ZoneId.of("Asia/Kolkata")).toEpochSecond();

Now, I want to generate the 'now' again from epochSecondNow:

LocalDateTime class has a method ' ofEpochSecond(long epochSecond,long nanoOfSecond, ZoneOffset zoneOffset)' which takes epoch second, nano of second and ZoneOffset as arguments.

I am not able to create ZoneOffset using "Asia/Kolkata". How should I make the ZoneOffset object for my zone in order to make use of 'ofEpochSecond' method. Is there any other way?

Thanks!

Answer 1

Try use with Instant.ofEpochSecond

Instant instant = Instant.ofEpochSecond(epochSecondNow);
ZonedDateTime atZone = instant.atZone(ZoneId.of("Asia/Kolkata"));
LocalDateTime localDateTime = atZone.toLocalDateTime();

If you want to use with system time zone, can do with ZoneId.systemDefault()