Java ZonedDateTime plusDays()

In this guide, you will learn about the ZonedDateTime plusDays() method in Java programming and how to use it with an example.

1. ZonedDateTime plusDays() Method Overview

Definition:

The plusDays() method of the ZonedDateTime class in Java is used to add the specified number of days to this ZonedDateTime. The calculation is done based on the local date-time, and the time zone is kept unchanged.

Syntax:

ZonedDateTime plusDays(long daysToAdd)

Parameters:

- daysToAdd: The number of days to add; may be negative.

Key Points:

- The plusDays() method returns a new ZonedDateTime instance with the specified number of days added.

- The method handles adjustments in the case of daylight saving time changes and other anomalies, ensuring accurate calculations.

- If the new date-time exceeds the supported range, a DateTimeException will be thrown.

- Adding zero days will have no effect and will return the same instance.

2. ZonedDateTime plusDays() Method Example

import java.time.ZonedDateTime;
import java.time.ZoneId;

public class ZonedDateTimePlusDaysExample {
    public static void main(String[] args) {
        // Create a ZonedDateTime instance
        ZonedDateTime zonedDateTime = ZonedDateTime.of(2023, 9, 20, 12, 34, 56, 0, ZoneId.of("Europe/Paris"));
        System.out.println("Original ZonedDateTime: " + zonedDateTime);

        // Adding 5 days to the original ZonedDateTime
        ZonedDateTime afterAddingDays = zonedDateTime.plusDays(5);
        System.out.println("After adding 5 days: " + afterAddingDays);

        // Adding a negative number of days (subtracting days)
        ZonedDateTime afterSubtractingDays = zonedDateTime.plusDays(-3);
        System.out.println("After subtracting 3 days: " + afterSubtractingDays);
    }
}

Output:

Original ZonedDateTime: 2023-09-20T12:34:56+02:00[Europe/Paris]
After adding 5 days: 2023-09-25T12:34:56+02:00[Europe/Paris]
After subtracting 3 days: 2023-09-17T12:34:56+02:00[Europe/Paris]

Explanation:

In the example, we created an original ZonedDateTime instance and used the plusDays() method to add and subtract days. Adding 5 days to the original date resulted in a new date of 2023-09-25, and subtracting 3 days resulted in a new date of 2023-09-17. The time and the time-zone remained unchanged in both cases.