Java 8 - How to convert Calendar to LocalDateTime?

1. Overview

In this article, You'll learn how to convert Calendar to LocalDateTime object in java 8 DateTime api. 

LocalDateTime api can be used completely replacement to the Date class as all features of Date functions are done in a simple and precise way such as adding minutes to the current date.

2. Example Program To Convert Calendar to LocalDateTime

To convert to LocalDateTime, you need to do the following steps.

Step 1:

First, Create a Calendar instance using Calendar.getInstance() method that returns Calendar object.

Step 2 :

Next, Get the time zone from the calendar instance using the calendar.getTimeZone() method.

Step 3:

Now, Get the ZoneId object from TimeZone class using timezone.toZoneId() method.

Step 4:

Finally, Invoke the LocalDateTime.ofInstant(calendar.toInstant(), zoneId) method with the calendar instant and zone id value.

package com.javaprogramto.java8.dates.conversion;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.Calendar;
import java.util.TimeZone;

public class CalenderToLocalDateTimeExample {

    public static void main(String[] args) {

        //Create a calender instance.
        Calendar calendar = Calendar.getInstance();

        System.out.println("Calender instance : "+calendar);

        // Getting the timezone
        TimeZone tz = calendar.getTimeZone();

        // Getting zone id
        ZoneId zoneId = tz.toZoneId();

        // conversion
        LocalDateTime localDateTime = LocalDateTime.ofInstant(calendar.toInstant(), zoneId);

        System.out.println("Local date time object  : "+localDateTime);

    }
}

Output:

Calender instance : java.util.GregorianCalendar[time=1596972628333,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Kolkata",offset=19800000,dstSavings=0,useDaylight=false,transitions=7,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2020,MONTH=7,WEEK_OF_YEAR=33,WEEK_OF_MONTH=3,DAY_OF_MONTH=9,DAY_OF_YEAR=222,DAY_OF_WEEK=1,DAY_OF_WEEK_IN_MONTH=2,AM_PM=1,HOUR=5,HOUR_OF_DAY=17,MINUTE=0,SECOND=28,MILLISECOND=333,ZONE_OFFSET=19800000,DST_OFFSET=0]
Local date time object  : 2020-08-09T17:00:28.333
3. Convert Calendar to LocalDate

package com.javaprogramto.java8.dates.conversion;

import java.time.LocalDate;
import java.time.ZoneId;
import java.util.Calendar;
import java.util.Date;

public class CalenderToLocalDateExample {

    public static void main(String[] args) {

        Calendar cal = Calendar.getInstance();
        Date input = cal.getTime();
        LocalDate la = input.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();

        System.out.println("Calender to LocalDate : "+la);
    }
}

Output:

Calender to LocalDate : 2020-08-09

4. Single Line Conversion from Calendar to LocalDateTime and LocalDate in Java 8

Finally, You can get the conversion to LocalDateTime and LocalDate in Java 8 in a single line. It is good practice to write in separate methods for reusing.

package com.javaprogramto.java8.dates.conversion;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.Calendar;

public class SingleLineCalenderToLocalDateTimeExample {

    public static void main(String[] args) {

        //Create a calender instance.
        Calendar calendar = Calendar.getInstance();


        LocalDateTime singleLineLocalDateTime = getLocalDateTime(calendar);
        LocalDate singleLineLocalDate = getLocalDate(calendar);

        System.out.println("Converted LocalDateTime : "+singleLineLocalDateTime);
        System.out.println("Converted LocalDate : "+singleLineLocalDate);

    }

    private static LocalDateTime getLocalDateTime(Calendar calendar){

        return  LocalDateTime.ofInstant(calendar.toInstant(), calendar.getTimeZone().toZoneId());
    }

    private static LocalDate getLocalDate(Calendar calendar){

        return  LocalDateTime.ofInstant(calendar.toInstant(), calendar.getTimeZone().toZoneId()).toLocalDate();
    }
}

Output:

Converted LocalDateTime : 2020-08-09T20:23:47.780
Converted LocalDate : 2020-08-09

5. Conclusion

In this article, You've learned how to convert Calendar Date object into LocalDateTime and LocalDate in Java 8.

And also can be converted LocalDateTime to LocalDate using toLocalDate() method.

Examples of programs shown are in GitHub.

CalenderToLocalDateExample.java

CalenderToLocalDateTimeExample.java

SingleLineCalenderToLocalDateTimeExample.java

LocalDateTime API

LocalDate API

Date.toLocalDate()

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