ZonedDateTime withDayOfYear() method in Java with Examples

withDayOfYear() method of a ZonedDateTime class used to alter day-of-year in this ZonedDateTime and return a copy of ZonedDateTime after this operation.This method operates on the local time-line, changing the day-of-year of the local date-time and after this operation local date-time is converted back to a ZonedDateTime, using the zone ID to obtain the offset. When converting back to ZonedDateTime, if the local date-time is in an overlap, then the offset will be retained if possible, otherwise, the earlier offset will be used. This instance is immutable and unaffected by this method call.

Syntax:

public ZonedDateTime withDayOfYear(int dayOfYear)

Parameters: This method accepts a single parameter dayOfYear which represents the day-of-year to set in the result, from 1 to 365-366.

Return value: This method returns a ZonedDateTime based on this date-time with the requested day.

Exception: This method throws DateTimeException if the day-of-year value is invalid, or if the day-of-year is invalid for the year-year.

Below programs illustrate the withDayOfYear() method:
Program 1:

// Java program to demonstrate
// ZonedDateTime.withDayOfYear() method

import java.time.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a ZonedDateTime object
        ZonedDateTime zoneddatetime
            = ZonedDateTime.parse(
                "2018-12-06T19:21:12.123+05:30[Asia/Calcutta]");

        // print instance
        System.out.println("ZonedDateTime before"
                           + " alter dayOfYear: "
                           + zoneddatetime);

        // alter dayOfYear to 200th day
        ZonedDateTime returnvalue
            = zoneddatetime.withDayOfYear(200);

        // print result
        System.out.println("ZonedDateTime after "
                           + "alter dayOfYear: "
                           + returnvalue);
    }
}

Output:

ZonedDateTime before alter dayOfYear: 2018-12-06T19:21:12.123+05:30[Asia/Calcutta]
ZonedDateTime after alter dayOfYear: 2018-07-19T19:21:12.123+05:30[Asia/Calcutta]

Program 2:

// Java program to demonstrate
// ZonedDateTime.withDayOfYear() method

import java.time.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a ZonedDateTime object
        ZonedDateTime zoneddatetime
            = ZonedDateTime.parse(
                "2018-10-25T23:12:31.123+02:00[Europe/Paris]");

        // print instance
        System.out.println("ZonedDateTime before"
                           + " alter dayOfYear: "
                           + zoneddatetime);

        // alter dayOfYear to 365
        ZonedDateTime returnvalue
            = zoneddatetime.withDayOfYear(365);

        // print result
        System.out.println("ZonedDateTime after "
                           + "alter dayOfYear: "
                           + returnvalue);
    }
}

Output:

ZonedDateTime before alter dayOfYear: 2018-10-25T23:12:31.123+02:00[Europe/Paris]
ZonedDateTime after alter dayOfYear: 2018-12-31T23:12:31.123+01:00[Europe/Paris]

Reference: https://docs.oracle.com/javase/10/docs/api/java/time/ZonedDateTime.html#withDayOfYear(int)