How to convert java.time.LocalDate to java.util.Date?

The following code snippet demonstrate how to convert java.time.LocalDate to java.util.Date and vice versa. In the first part of the code snippet we convert LocalDate to Date and back to LocalDate object. On the second part we convert LocalDateTime to Date and back to LocalDateTime object.

package org.kodejava.example.datetime;

import java.time.*;
import java.util.Date;

public class LocalDateToDate {
    public static void main(String[] args) {
        // Convert java.time.LocalDate to java.util.Date and back to
        // java.time.LocalDate
        LocalDate localDate = LocalDate.now();
        System.out.println("LocalDate = " + localDate);

        Date date1 = Date.from(localDate.atStartOfDay(ZoneId.systemDefault()).toInstant());
        System.out.println("Date      = " + date1);

        localDate = date1.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
        System.out.println("LocalDate = " + localDate);
        System.out.println();

        // Convert java.time.LocalDateTime to java.util.Date and back to
        // java.time.LocalDateTime
        LocalDateTime localDateTime = LocalDateTime.now();
        System.out.println("LocalDateTime = " + localDateTime);

        Date date2 = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
        System.out.println("Date          = " + date2);

        localDateTime = date2.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
        System.out.println("LocalDateTime = " + localDateTime);
    }
}

The result of the code snippet:

LocalDate = 2017-02-14
Date      = Tue Feb 14 00:00:00 WITA 2017
LocalDate = 2017-02-14

LocalDateTime = 2017-02-14T10:34:49.562
Date          = Tue Feb 14 10:34:49 WITA 2017
LocalDateTime = 2017-02-14T10:34:49.562

How do I convert between old Date and Calendar object with the new Java 8 Date Time?

In this example we will learn how to convert the old java.util.Date and java.util.Calendar objects to the new Date Time introduced in Java 8. The first method in the code snippet below dateToNewDate() show conversion of java.util.Date while the calendarToNewDate() show the conversion of java.util.Calendar.

The java.util.Date and java.util.Calendar provide a toInstant() method to convert the objects to the new Date Time API class of the java.time.Instant. To convert the old date into the Java 8 LocalDate, LocalTime and LocalDateTime we first can create an instance of ZonedDateTime using the atZone() method of the Instant class.

ZonedDateTime zonedDateTime = instant.atZone(ZoneId.systemDefault());

From an instance of ZonedDateTime class we can call the toLocalDate(), toLocalTime() and toLocalDateTime() to get instance of LocalDate, LocalTime and LocalDateTime.

To convert back from the new Java 8 date to the old java.util.Date we can use the Date.from() static factory method and passing and instance of java.time.Instant that we can obtains by calling the following code.

Instant instant1 = dateTime.atZone(ZoneId.systemDefault()).toInstant();
Date now1 = Date.from(instant1);

Here are the complete code snippet to convert java.util.Date to the new Java 8 Date Time.

private static void dateToNewDate() {
    Date now = new Date();
    Instant instant = now.toInstant();

    ZonedDateTime zonedDateTime = instant.atZone(ZoneId.systemDefault());

    LocalDate date = zonedDateTime.toLocalDate();
    LocalTime time = zonedDateTime.toLocalTime();
    LocalDateTime dateTime = zonedDateTime.toLocalDateTime();

    Instant instant1 = dateTime.atZone(ZoneId.systemDefault()).toInstant();
    Date now1 = Date.from(instant1);

    System.out.println("java.util.Date          = " + now);
    System.out.println("java.time.LocalDate     = " + date);
    System.out.println("java.time.LocalTime     = " + time);
    System.out.println("java.time.LocalDateTime = " + dateTime);
    System.out.println("java.util.Date          = " + now1);
    System.out.println();
}

The steps for converting from the java.util.Calendar to the new Java 8 date can be seen in the code snippet below. As with java.util.Date the Calendar class provide toInstant() method to convert the calendar to java.time.Instant object.

Using the LocalDateTime.ofInstant() method we can create a LocalDateTime object from the instant object. By having the LocalDateTime object we can then get an instance of LocalDate and LocalTime by calling the toLocalDate() and toLocalTime() method.

Finally to convert back to java.util.Calendar we can use the GregorianCalendar.from() static factory method which require an instance of ZonedDateTime to be passed as a parameter. To get an instance of ZonedDateTime we can call LocalDateTime.atZone() method. You can see the complete code in the code snippet below.

private static void calendarToNewDate() {
    Calendar now = Calendar.getInstance();

    LocalDateTime dateTime = LocalDateTime.ofInstant(now.toInstant(),
            ZoneId.systemDefault());

    LocalDate date = dateTime.toLocalDate();
    LocalTime time = dateTime.toLocalTime();

    ZonedDateTime zonedDateTime = dateTime.atZone(ZoneId.systemDefault());
    Calendar now1 = GregorianCalendar.from(zonedDateTime);

    System.out.println("java.util.Calendar      = " + now);
    System.out.println("java.time.LocalDateTime = " + dateTime);
    System.out.println("java.time.LocalDate     = " + date);
    System.out.println("java.time.LocalTime     = " + time);
    System.out.println("java.util.Calendar      = " + now1);
}

Below is the main Java class to run the code snippet. You must place the above methods inside this class to run the code snippet.

package org.kodejava.example.datetime;

import java.time.*;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class LegacyDateCalendarToNewDateExample {
    public static void main(String[] args) {
        dateToNewDate();
        calendarToNewDate();
    }
}

Here are the result of the code snippet above. The first group is conversion the java.util.Date to the new Date Time API. The second group is conversion from the java.util.Calendar to the new Date Time API.

java.util.Date          = Mon Feb 01 11:09:55 WITA 2016
java.time.LocalDate     = 2016-02-01
java.time.LocalTime     = 11:09:55.746
java.time.LocalDateTime = 2016-02-01T11:09:55.746
java.util.Date          = Mon Feb 01 11:09:55 WITA 2016

java.util.Calendar      = java.util.GregorianCalendar[time=1454296195871,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Makassar",offset=28800000,dstSavings=0,useDaylight=false,transitions=5,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2016,MONTH=1,WEEK_OF_YEAR=6,WEEK_OF_MONTH=1,DAY_OF_MONTH=1,DAY_OF_YEAR=32,DAY_OF_WEEK=2,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=11,HOUR_OF_DAY=11,MINUTE=9,SECOND=55,MILLISECOND=871,ZONE_OFFSET=28800000,DST_OFFSET=0]
java.time.LocalDateTime = 2016-02-01T11:09:55.871
java.time.LocalDate     = 2016-02-01
java.time.LocalTime     = 11:09:55.871
java.util.Calendar      = java.util.GregorianCalendar[time=1454296195871,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Makassar",offset=28800000,dstSavings=0,useDaylight=false,transitions=5,lastRule=null],firstDayOfWeek=2,minimalDaysInFirstWeek=4,ERA=1,YEAR=2016,MONTH=1,WEEK_OF_YEAR=5,WEEK_OF_MONTH=1,DAY_OF_MONTH=1,DAY_OF_YEAR=32,DAY_OF_WEEK=2,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=11,HOUR_OF_DAY=11,MINUTE=9,SECOND=55,MILLISECOND=871,ZONE_OFFSET=28800000,DST_OFFSET=0]

How do I convert string to Date in GMT timezone?

The following code snippet convert a string representation of a date into a java.util.Date object and the timezone is set to GMT. To parse the string so that the result is in GMT you must set the TimeZone of the DateFormat object into GMT.

package org.kodejava.example.text;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

public class WithTimezoneStringToDate {
    public static void main(String[] args) {
        // Create a DateFormat and set the timezone to GMT.
        DateFormat df = new SimpleDateFormat("E, dd MMM yyyy HH:mm:ss z");
        df.setTimeZone(TimeZone.getTimeZone("GMT"));

        try {
            // Convert string into Date
            Date today = df.parse("Mon, 16 Apr 2018 00:00:00 GMT+08:00");
            System.out.println("Today = " + df.format(today));
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

The code snippet above print the following output:

Today = Sun, 15 Apr 2018 16:00:00 GMT

How do I get pattern string of a SimpleDateFormat?

To format a java.util.Date object we use the SimpleDateFormat class. To get back the string pattern that were used to format the date we can use the toPattern() method of this class.

package org.kodejava.example.text;

import java.text.SimpleDateFormat;
import java.util.Date;

public class SimpleDateFormatToPattern {
    public static void main(String[] args) {
        SimpleDateFormat format = new SimpleDateFormat("EEEE, dd/MM/yyyy");

        // Gets a pattern string describing this date format used by the
        // SimpleDateFormat object.
        String pattern = format.toPattern();

        System.out.println("Pattern = " + pattern);
        System.out.println("Date    = " + format.format(new Date()));
    }
}

The result of the program will be as follow:

Pattern = EEEE, dd/MM/yyyy
Date    = Monday, 16/04/2018

How do I create JSpinner component with date value?

The SpinnerDateModel allow us to display and select date information from the JSpinner component. By default the initial value of the model will be set to the current date. To change it we can call the setValue method of the JSpinner object.

package org.kodejava.example.swing;

import javax.swing.*;
import java.awt.*;
import java.util.GregorianCalendar;
import java.util.Calendar;

public class JSpinnerDate extends JFrame {
    public JSpinnerDate() {
        initializeUI();
    }

    private void initializeUI() {
        setSize(300, 300);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        // Create a SpinnerDateModel with current date as the initial value.
        SpinnerDateModel model = new SpinnerDateModel();

        // Set the spinner value to June 8, 2008.
        JSpinner spinner = new JSpinner(model);
        Calendar calendar = new GregorianCalendar(2008, Calendar.JUNE, 8);
        spinner.setValue(calendar.getTime());

        getContentPane().add(spinner, BorderLayout.NORTH);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JSpinnerDate().setVisible(true);
            }
        });
    }
}

How do I format a message that contains date information?

This example demonstrate how you can use the java.text.MessageFormat class to format a message with a date information in it.

package org.kodejava.example.text;

import java.util.Date;
import java.util.Calendar;
import java.util.Locale;
import java.text.MessageFormat;

public class MessageFormatDate {
    public static void main(String[] args) {
        Date today = new Date();
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.DATE, 7);

        Date nextWeek = calendar.getTime();

        // We want the message to be is Locale.US
        Locale.setDefault(Locale.US);

        // Format a date, the time value is included
        String message = MessageFormat.format("Today is {0} and next " +
            "week is {1}", today, nextWeek);
        System.out.println(message);

        // Format a date and display only the date portion
        message = MessageFormat.format("Today is {0,date} and next " +
            "week is {1,date}", today, nextWeek);
        System.out.println(message);

        // Format a date using a short format (eg. dd/MM/yyyy)
        message = MessageFormat.format("Today is {0,date,short} and " +
            "next week is {1,date,short}", today, nextWeek);
        System.out.println(message);

        // Format a date using a medium format, it display the month long name,
        // but using a two digit date and year.
        message = MessageFormat.format("Today is {0,date,medium} and " +
            "next week is {1,date,medium}", today, nextWeek);
        System.out.println(message);

        // Format a date using a long format, two digit for date, a long month
        // name and a four digit year.
        message = MessageFormat.format("Today is {0,date,long} and " +
            "next week is {1,date,long}", today, nextWeek);
        System.out.println(message);

        // Format a date using a full format, the same as above plus a full day
        // name.
        message = MessageFormat.format("Today is {0,date,full} and " +
            "next week is {1,date,full}", today, nextWeek);
        System.out.println(message);

        // Format a date using a custom pattern.
        message = MessageFormat.format("Today is {0,date,dd-MM-yyyy} and " +
            "next week is {1,date,dd-MM-yyyy}", today, nextWeek);
        System.out.println(message);
    }
}

The above program produces:

Today is 2/15/18, 8:57 PM and next week is 2/22/18, 8:57 PM
Today is Feb 15, 2018 and next week is Feb 22, 2018
Today is 2/15/18 and next week is 2/22/18
Today is Feb 15, 2018 and next week is Feb 22, 2018
Today is February 15, 2018 and next week is February 22, 2018
Today is Thursday, February 15, 2018 and next week is Thursday, February 22, 2018
Today is 15-02-2018 and next week is 22-02-2018

How do I add hours, minutes or seconds to a date?

This example shows you how to add or subtract hours, minutes or seconds to a date using the java.util.Calendar object.

package org.kodejava.example.util;

import java.util.Calendar;

public class DateAddSubtract {
    public static void main(String[] args) {
        // Gets a calendar using the default time zone and locale. The
        // Calendar returned is based on the current time in the default
        // time zone with the default locale.
        Calendar calendar = Calendar.getInstance();
        System.out.println("Original = " + calendar.getTime());

        // Substract 2 hour from the current time
        calendar.add(Calendar.HOUR, -2);

        // Add 30 minutes to the calendar time
        calendar.add(Calendar.MINUTE, 30);

        // Add 300 seconds to the calendar time
        calendar.add(Calendar.SECOND, 300);
        System.out.println("Updated  = " + calendar.getTime());
    }
}

The output of the code snippet:

Original = Tue Oct 31 09:31:34 CST 2017
Updated  = Tue Oct 31 08:06:34 CST 2017

How do I format date using a locale based format?

The code below demonstrate how to format date information for a specific locale. In the example utilize the java.text.SimpleDateFormat class.

package org.kodejava.example.text;

import java.util.Locale;
import java.util.Date;
import java.text.SimpleDateFormat;

public class FormatDateLocale {
    public static void main(String[] args) {
        // Defines an array of Locale we are going to use for
        // formatting date information.
        Locale[] locales = new Locale[] {
            Locale.JAPAN,
            Locale.CHINA,
            Locale.KOREA,
            Locale.TAIWAN,
            Locale.ITALY,
            Locale.FRANCE,
            Locale.GERMAN
        };

        // Get an instance of current date time
        Date today = new Date();

        // Iterates the entire Locale defined above and create a long
        // formatted date using the SimpleDateFormat.getDateInstance()
        // with the format, the Locale and the date information.
        for (Locale locale : locales) {
            System.out.printf("Date format in %s = %s%n",
                locale.getDisplayName(), SimpleDateFormat.getDateInstance(
                    SimpleDateFormat.LONG, locale).format(today));
        }
    }
}

The result of our code are:

Date format in Japanese (Japan) = 2018年2月15日
Date format in Chinese (China) = 2018年2月15日
Date format in Korean (South Korea) = 2018년 2월 15일
Date format in Chinese (Taiwan) = 2018年2月15日
Date format in Italian (Italy) = 15 febbraio 2018
Date format in French (France) = 15 février 2018
Date format in German = 15. Februar 2018

How do I know if a date is after another date?

This example demonstrate Date‘s class after() method to check if a date is later than another date.

package org.kodejava.example.util;

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

public class DateCompareAfter {
    public static void main(String[] args) {
        // Get current date
        Date today = new Date();

        // Add 1 day from the current date.
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.DATE, 1);
        Date tomorrow = calendar.getTime();

        // Tests if this date is after the specified date. This method will
        // return true if the value time represented by the tomorrow object
        // is later than today.
        if (tomorrow.after(today)) {
            System.out.println(tomorrow + " is after " + today);
        }
    }
}

The result of the code snippet above is:

Mon Oct 30 21:20:24 WITA 2017 is after Sun Oct 29 21:20:24 WITA 2017

How do I know if a date is before another date?

This example demonstrate Date‘s class before() method to check if a date is earlier than another date.

package org.kodejava.example.util;

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

public class DateCompareBefore {
    public static void main(String[] args) {
        // Get current date
        Date today = new Date();

        // Subtract 1 day from the current date.
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.DATE, -1);
        Date yesterday = calendar.getTime();

        // Tests if this date is before the specified date. This method will
        // return true if the value time represented by the yesterday object
        // is earlier than today.
        if (yesterday.before(today)) {
            System.out.println(yesterday + " is before " + today);
        }
    }
}

The result of the code snippet above is:

Sat Oct 28 21:16:33 WITA 2017 is before Sun Oct 29 21:16:33 WITA 2017