Add date on Calendar

Question

I try to create the code below. today is 7/2/07, but when I -2 days it shows 6/31/07. but there is no such a date. what do I do to make it go to 6/30/07?
Calendar now = Calendar.getInstance();
Calendar calendar;
calendar = (Calendar) now.clone();
//date of calendar is 6/2/07
calendar.add(Calendar.MONTH, 1);
//date of calendar is 7/2/07
calendar.add(Calendar.DAY_OF_YEAR, -2);
//date of calendar is 6/31/07

Answer 1

I had to change EST to PST time and was not able to find method to do that so I created one dateAdd().
To add date you need to pass date as string in the format yyyyMMddHHmmss, string date part such as y, M, d, h, m, or s and positive or negative integer to get future or past date. You can change date format in the code and then you will pass according date string, or add parameter to specify format for your date. Ok, you got the idea.
import java.text.SimpleDateFormat;
import java.text.DateFormat;
import java.util.*;
private String dateAdd(String sDate, String sPart, int i){
DateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");
Date d1 = new Date ();
String sStr = "";
if (StringUtils.isNumeric(sDate)){
if (sDate.length()>13){
System.out.println("sD = " + sDate);
sStr = sDate.substring(14);
sDate= sDate.substring(0,14);
}else{
sDate = StringUtils.rightPad(sDate, 14, "0");
try{
d1 = df.parse(sDate);
Calendar cal = Calendar.getInstance();
cal.setTime(d1);
if(sPart.equals("s")){
cal.add(Calendar.SECOND, i);
else if(sPart.equals("m")){
cal.add(Calendar.MINUTE, i);
else if(sPart.equals("h")){
cal.add(Calendar.HOUR, i);
else if (sPart.equals("d")){
cal.add(Calendar.DAY_OF_MONTH, i);
else if(sPart.equals("M")){
cal.add(Calendar.MONTH, i);
else if(sPart.equals("y")){
cal.add(Calendar.YEAR, i);
sDate = df.format(cal.getTime())+ sStr;
} catch (Exception ex) {
ex.printStackTrace();
return sDate;
Enjoy dateAdding.
Thank you.