Here you can find the source of minusDayOfWeek(int dow, long days)
public static int minusDayOfWeek(int dow, long days)
//package com.java2s; /*/* w w w. ja va2s.c o m*/ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ public class Main { public static int minusDayOfWeek(int dow, long days) { return plusDayOfWeek(dow, -(days % 7)); } public static int plusDayOfWeek(int dow, long days) { int amount = (int) (days % 7); return (dow - 1 + (amount + 7)) % 7 + 1; } }