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Here is how to do it without Joda Time:

import java.text.DateFormat;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Calendar;

import java.util.Date;



public class Main {



    public static String previousDateString(String dateString) 

            throws ParseException {

        // Create a date formatter using your format string

        DateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");



        // Parse the given date string into a Date object.

        // Note: This can throw a ParseException.

        Date myDate = dateFormat.parse(dateString);



        // Use the Calendar class to subtract one day

        Calendar calendar = Calendar.getInstance();

        calendar.setTime(myDate);

        calendar.add(Calendar.DAY_OF_YEAR, -1);



        // Use the date formatter to produce a formatted date string

        Date previousDate = calendar.getTime();

        String result = dateFormat.format(previousDate);



        return result;

    }



    public static void main(String args) {

        String dateString = "20100316";



        try {

            // This will print 20100315

            System.out.println(previousDateString(dateString));

        } catch (ParseException e) {

            System.out.println("Invalid date string");

            e.printStackTrace();

        }

    }

}

You can use:

    Calendar cal  = Calendar.getInstance();

    //subtracting a day

    cal.add(Calendar.DATE, -1);



    SimpleDateFormat s = new SimpleDateFormat("yyyyMMdd");

    String result = s.format(new Date(cal.getTimeInMillis()));

It's much harder than it should be in Java without library support.

You can parse the given String into a Date object using an instance of the SimpleDateFormat class.

Then you can use Calendar's add() to subtract one day.

Then you can use SimpleDateFormat's format() to get the formatted date as a String.

The Joda Time library a much easier API.

use SimpleDateFormat to parse the String to Date, then subtract one day. after that convert the date to String again.

HI,

I want to get 20 days previous, to current date,

 Calendar cal = Calendar.getInstance();

    Calendar xdate = (Calendar)cal.clone();

xdate.set(Calendar.DAY_OF_YEAR, - 20);



System.out.println(" Current Time "+ cal.getTime().toString());

System.out.println(" X Time "+ xdate.getTime().toString());

I had some UN Expected result, When i tried on Jan 11th,

Current Time Tue Jan 11 12:32:16 IST 2011
X Time Sat Dec 11 12:32:16 IST 2010

Calendar cal = Calendar.getInstance();

Calendar xdate = (Calendar)cal.clone();

xdate.set(Calendar.DAY_OF_YEAR,cal.getTime().getDate() - 20 );



System.out.println(" Current Time "+ cal.getTime().toString());

System.out.println(" X Time "+ xdate.getTime().toString());

This code solved my Problem.

If you are willing to use the 3rd-party utility, Joda-Time, here is some example code using Joda-Time 2.3 on Java 7. Takes just two lines.

String dateAsString = "20130101";

org.joda.time.LocalDate someDay =  org.joda.time.LocalDate.parse(dateAsString, org.joda.time.format.DateTimeFormat.forPattern("yyyymmdd"));

org.joda.time.LocalDate dayBefore = someDay.minusDays(1);

See the results:

System.out.println("someDay: " + someDay );

System.out.println("dayBefore: " + dayBefore );

When run:

someDay: 2013-01-01

dayBefore: 2012-12-31

This code assumes you have no time zone. Lacking a time zone is rarely a good thing, but if that's your case, that code may work for you. If you do have a time zone, use a DateTime object instead of LocalDate.

About that example code and about Joda-Time…

// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.



// Joda-Time - The popular alternative to Sun/Oracle's notoriously bad date, time, and calendar classes bundled with Java 7 and earlier.

// http://www.joda.org/joda-time/



// Joda-Time will become outmoded by the JSR 310 Date and Time API introduced in Java 8.

// JSR 310 was inspired by Joda-Time but is not directly based on it.

// http://jcp.org/en/jsr/detail?id=310



// By default, Joda-Time produces strings in the standard ISO 8601 format.

// https://en.wikipedia.org/wiki/ISO_8601

you can create a generic method which takes

   - Date (String)  (current date or from date),

   - Format (String) (your desired fromat) and

   - Days (number of days before(-ve value) or after(+ve value))

as input and return your desired date in required format.

following method can resolve this problem.

public String getRequiredDate(String date , String format ,int days){

        try{

         final Calendar cal = Calendar.getInstance();

            cal.setTime(new SimpleDateFormat(format).parse(date));

            cal.add(Calendar.DATE, days);

            SimpleDateFormat sdf = new SimpleDateFormat(format);

            date = sdf.format(cal.getTime());

        }

        catch(Exception ex){

            logger.error(ex.getMessage(), ex);

        }

        return date;

    }

}

Calendar cal2 = Calendar.getInstance();

cal2.add(Calendar.YEAR, -1);

Date dt2 = new Date(cal2.getTimeInMillis());

System.out.println(dt2);