Here you can find the source of dateAfterDate(Date date, long days)
public static Date dateAfterDate(Date date, long days)
//package com.java2s; import java.util.Date; public class Main { public static Date dateAfterDate(Date date, long days) { long d = date.getTime(); d += days * 86400000;/* w w w . j a va 2 s. com*/ return new java.util.Date(d); } }