Addition and Subtraction of Dates in Java

Question

How can we add or subtract date in java? For instance java.sql.Date and formatted like this: yyyy-MM-dd , how can i Add 5 months from that? I've seen in some tutorial that they are using Calendar , can we set date on it? Please Help.

Example: 2012-01-01 when added 5 months will become 2012-06-01 .

PS: I'm a.Net Programmer and slowly learning to Java environment.

Answer 1

First of all you have to convert your String date to java.util.Date , than you have to use java.util.Calendar to manipulate dates. It is also possible to do math with millis, but I do not recommend this.

public static void main( final String[] args ) throws ParseException {
    final String sdate = "2012-01-01";
    final SimpleDateFormat df = new SimpleDateFormat( "yyyy-MM-dd" );
    final Date date = df.parse( sdate ); // conversion from String
    final java.util.Calendar cal = GregorianCalendar.getInstance();
    cal.setTime( date );
    cal.add( GregorianCalendar.MONTH, 5 ); // date manipulation
    System.out.println( "result: " + df.format( cal.getTime() ) ); // conversion to String
}

Answer 2

Stear clear of the built-in Date class for date math. Take a look at JodaTime, which has a much better API for this kind of thing.

Answer 3

Use Calendar

Calendar cal = Calendar.getInstance();
cal.add(Calendar.MONTH, 5);

Answer 4

To convert a Date to a Calendar, use:

Date date = your_date_here;

Calendar cal = Calendar.getInstance();
cal.setTime(date);

Then use the calendar arithmetic functions to add/subtract:

cal.add(Calendar.MONTH, 5);

Answer 5

Or, Convert the date to time in milis. Do the math, and convert the millis back to a date.

Answer 6

use CalenderUtils from google's package GWT.

import com.google.gwt.user.datepicker.client.CalendarUtil;

...

//now
Date d = new Date();
// Now + 2 months
CalendarUtil.addMonthsToDate(d, 2);

Answer 7

Another option is the DateUtils class from the 3rd party Apache Commons library collection. Example:

Date d = DateUtils.parseDate("2012-01-01", "yyyy-MM-dd");
Date d2 = DateUtils.addMonths(d, 5);
System.out.println("Old date + 5 months = " + d2);

Answer 8

There are various ways. One of them could be with joda.time . This does not answer the question by using Calendar but one of the other approach if needed by someone. :D

import java.sql.Date;
import org.joda.time.DateTime;
//
DateTime datetime = new DateTime("2012-01-01");
Date dt = new Date(datetime.plusMonths(5).toDate().getTime());
System.out.println(dt);
// This gives output as 2012-06-01

PS: Happy coding with Java

Answer 9

java.time

The accepted answer uses java.util date-time API and SimpleDateFormat which was the correct thing to do in 2012. In Mar 2014, the java.util date-time API and their formatting API, SimpleDateFormat were supplanted by the modern date-time API . Since then, it is highly recommended to stop using the legacy date-time API.

Solution using java.time , the modern date-time API:

You do not need a DateTimeFormatter for your date string: java.time API is based on ISO 8601 and therefore you do not need to specify a DateTimeFormatter to parse a date-time string which is already in ISO 8601 format eg your date string, 2012-01-01 which can be parsed directly into a LocalDate instance, that contains just date units.

Having parsed the date string into LocalDate , you can add or subtract different date units eg years, months, days etc. to it.

Demo :

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;

class Main {
    public static void main(String args[]) {
        LocalDate date = LocalDate.parse("2012-01-01");
        System.out.println(date);

        LocalDate afterFiveMonths = date.plusMonths(5);
        LocalDate beforeFiveMonths = date.minusMonths(5);
        System.out.println(afterFiveMonths);
        System.out.println(beforeFiveMonths);

        // Alternatively,
        afterFiveMonths = date.plus(5, ChronoUnit.MONTHS);
        beforeFiveMonths = date.minus(5, ChronoUnit.MONTHS);
        System.out.println(afterFiveMonths);
        System.out.println(beforeFiveMonths);
    }
}

Output :

2012-01-01
2012-06-01
2011-08-01
2012-06-01
2011-08-01

ONLINE DEMO

Learn more about the modern Date-Time API from Trail: Date Time .

Answer 10

完成日期添加的完整程序位于http://dwbitechguru.blogspot.ca/2014/09/jave-program-to-add-or-substract-dates.html