Java 8 examples to show you how to convert from Instant to ZonedDateTime
1. Instant -> ZonedDateTime
Example to convert a Instant UTC+0 to a Japan ZonedDateTime UTC+9
InstantZonedDateTime1.java
package com.mkyong.date;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
public class InstantZonedDateTime1 {
public static void main(String[] argv) {
// Z = UTC+0
Instant instant = Instant.now();
System.out.println("Instant : " + instant);
// Japan = UTC+9
ZonedDateTime jpTime = instant.atZone(ZoneId.of("Asia/Tokyo"));
System.out.println("ZonedDateTime : " + jpTime);
System.out.println("OffSet : " + jpTime.getOffset());
}
}
Output
Instant : 2016-08-18T06:17:10.225Z
LocalDateTime : 2016-08-18T06:17:10.225
2. ZonedDateTime -> Instant
Convert the Japan ZonedDateTime UTC+9 back to a Instant UTC+0/Z, review the result, the offset is taken care automatically.
InstantZonedDateTime2.java
package com.mkyong.date;
import java.time.*;
public class InstantZonedDateTime2 {
public static void main(String[] argv) {
LocalDateTime dateTime = LocalDateTime.of(2016, Month.AUGUST, 18, 6, 57, 38);
// UTC+9
ZonedDateTime jpTime = dateTime.atZone(ZoneId.of("Asia/Tokyo"));
System.out.println("ZonedDateTime : " + jpTime);
// Convert to instant UTC+0/Z , java.time helps to reduce 9 hours
Instant instant = jpTime.toInstant();
System.out.println("Instant : " + instant);
}
}
Output
ZonedDateTime : 2016-08-18T06:57:38+09:00[Asia/Tokyo]
Instant : 2016-08-17T21:57:38Z
References
- Wikipedia – ISO 8601 date format
- Instant JavaDoc
- ZoneddateTime JavaDoc