CODEWITHSUNDEEP
java-8localdatejava.time.instantjava-time
JL Gradley
JL Gradley

Reputation: 2031

How to convert from Instant to LocalDate

I have an Instant coming from a source that should, according to the specs, be a LocalDate, but don't see any methods in the LocalDate class to convert the Instant to a LocalDate.

What is the best way to do this?

Upvotes: 131

Views: 177544

Answers (6)

Rob C
Rob C

Reputation: 2441

Java 9+

LocalDate.ofInstant(...) arrived in Java 9.

Instant instant = Instant.parse("2020-01-23T00:00:00Z");
ZoneId zone = ZoneId.of("America/Edmonton");
LocalDate date = LocalDate.ofInstant(instant, zone);

See code run live at IdeOne.com.

Notice the date is 22nd rather than 23rd as that time zone uses an offset several hours before UTC.

2020-01-22

Java 8

If you are using Java 8, then you could use ZonedDateTime's toLocalDate() method:

yourInstant.atZone(yourZoneId).toLocalDate()

Upvotes: 209

t0r0X
t0r0X

Reputation: 4802

Complete running example, Java 8 compatible:

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;

class Scratch {

  public static void main(String[] args) {
    Instant now = Instant.now();
    LocalDateTime ldt = now.atZone(ZoneId.systemDefault()).toLocalDateTime();
    System.out.println(ldt);
  }
}

Upvotes: 1

Awais Yousaf
Awais Yousaf

Reputation: 33

 Instant instant = Instant.now();   
 LocalDate localDate = LocalDate.ofInstant(instant, ZoneOffset.UTC);

the above code worked for me.

Upvotes: 1

Krzysiek Przygudzki
Krzysiek Przygudzki

Reputation: 627

Other answers provided the mechanics for the transformation, but I wanted to add some background on the meaning of such transformation which hopefully helps explain why it works the way it works.

LocalDate and Instant seem similar – they both hold date(/time) information without the time zone information. However, they have quite a different meaning.

Instant represents a point in time unambiguously. The representation does not explicitly contain any time zone, but implicitly it refers to the UTC time line.

LocalDateTime (and LocalDate) is ambiguous, because it represents a point in the local timeline, which implicitly refers to the local time zone.

So, in order to correctly transform an Instant into a LocalDateTime (conceptually – some of these steps are bundled together into a single operation in the implementation) you need to:
1. convert the Instant into a ZonedDateTime by applying the UTC time zone info
2. change the time zone from UTC to the local time zone (which implies applying the relevant time zone offset) which gives you another ZonedDateTime (with different time zone)
3. convert the ZonedDateTime into a LocalDateTime which makes the time zone implicit (local) by removing the time zone info.

Finally, you can drop the time-part of LocalDateTime and end up with the LocalDate.

Upvotes: 44

Robbo_UK
Robbo_UK

Reputation: 12149

If using java 8 you can do the following

Instant instantOfNow = Instant.now();
LocalDate localDate 
    = LocalDateTime.ofInstant(instantOfNow, ZoneOffset.UTC).toLocalDate();

Upvotes: 25

Eugene
Eugene

Reputation: 121068

You need to ask yourself at what zone offset you want to transform it to most probably and when you know the answer to that:

LocalDate.ofInstant(yourInstant, yourZoneOffSet)

EDIT

just realized that this is only possible since java-9, for a pre-java9 see the other answer

Upvotes: 8

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