How do I set the time of java.util.Date instance to 00:00:00?

The following code snippet shows you how to remove time information from the java.util.Date object. The static method removeTime() in the code snippet below will take a Date object as parameter and will return a new Date object where the hour, minute, second and millisecond information hasbeen reset to zero. To do this, we use the java.util.Calendar. To remove time information, we set the calendar fields of Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND to zero.

package org.kodejava.util;

import java.util.Calendar;
import java.util.Date;

public class DateRemoveTime {
    public static void main(String[] args) {
        System.out.println("Now = " + removeTime(new Date()));
    }

    private static Date removeTime(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        return calendar.getTime();
    }
}

The result of the code snippet above is:

Now = Sat Nov 20 00:00:00 CST 2021

In the above code:

1. An instance of Calendar is created using Calendar.getInstance().
2. We set the Calendar time using setTime() method and pass the date object.
3. The time fields (HOUR_OF_DAY, MINUTE, SECOND, MILLISECOND) are set to zero. Calendar.HOUR_OF_DAY is used for 24-hour clock.
4. The resulting Calendar instances time value is printed which should now represent the start of the day.