1 2 /* ==================================================================== 3 * The Apache Software License, Version 1.1 4 * 5 * Copyright (c) 2002 The Apache Software Foundation. All rights 6 * reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in 17 * the documentation and/or other materials provided with the 18 * distribution. 19 * 20 * 3. The end-user documentation included with the redistribution, 21 * if any, must include the following acknowledgment: 22 * "This product includes software developed by the 23 * Apache Software Foundation (http://www.apache.org/)." 24 * Alternately, this acknowledgment may appear in the software itself, 25 * if and wherever such third-party acknowledgments normally appear. 26 * 27 * 4. The names "Apache" and "Apache Software Foundation" and 28 * "Apache POI" must not be used to endorse or promote products 29 * derived from this software without prior written permission. For 30 * written permission, please contact apache@apache.org. 31 * 32 * 5. Products derived from this software may not be called "Apache", 33 * "Apache POI", nor may "Apache" appear in their name, without 34 * prior written permission of the Apache Software Foundation. 35 * 36 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED 37 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 38 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 39 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR 40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 42 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 43 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 44 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 45 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 46 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 47 * SUCH DAMAGE. 48 * ==================================================================== 49 * 50 * This software consists of voluntary contributions made by many 51 * individuals on behalf of the Apache Software Foundation. For more 52 * information on the Apache Software Foundation, please see 53 * <http://www.apache.org/>. 54 */ 55 56 /* 57 * DateUtil.java 58 * 59 * Created on January 19, 2002, 9:30 AM 60 */ 61 package org.apache.poi.hssf.usermodel; 62 63 import java.util.Calendar; 64 import java.util.Date; 65 import java.util.GregorianCalendar; 66 67 /** 68 * Contains methods for dealing with Excel dates. 69 * 70 * @author Michael Harhen 71 * @author Glen Stampoultzis (glens at apache.org) 72 */ 73 74 public class HSSFDateUtil 75 { 76 private HSSFDateUtil() 77 { 78 } 79 80 private static final int BAD_DATE = 81 -1; // used to specify that date is invalid 82 private static final long DAY_MILLISECONDS = 24 * 60 * 60 * 1000; 83 private static final double CAL_1900_ABSOLUTE = 84 ( double ) absoluteDay(new GregorianCalendar(1900, Calendar 85 .JANUARY, 1)) - 2.0; 86 87 /** 88 * Given a Date, converts it into a double representing its internal Excel representation, 89 * which is the number of days since 1/1/1900. Fractional days represent hours, minutes, and seconds. 90 * 91 * @return Excel representation of Date (-1 if error - test for error by checking for less than 0.1) 92 * @param date the Date 93 */ 94 95 public static double getExcelDate(Date date) 96 { 97 Calendar calStart = new GregorianCalendar(); 98 99 calStart.setTime( 100 date); // If date includes hours, minutes, and seconds, set them to 0 101 if (calStart.get(Calendar.YEAR) < 1900) 102 { 103 return BAD_DATE; 104 } 105 else 106 { 107 calStart = dayStart(calStart); 108 double fraction = (date.getTime() - calStart.getTime().getTime()) 109 / ( double ) DAY_MILLISECONDS; 110 111 return fraction + ( double ) absoluteDay(calStart) 112 - CAL_1900_ABSOLUTE; 113 } 114 } 115 116 /** 117 * Given a excel date, converts it into a Date. 118 * 119 * @param date the Excel Date 120 * 121 * @return Java representation of a date (null if error) 122 */ 123 124 public static Date getJavaDate(double date) 125 { 126 if (isValidExcelDate(date)) 127 { 128 int wholeDaysSince1900 = ( int ) Math.floor(date); 129 GregorianCalendar calendar = new GregorianCalendar(1900, 130 0, wholeDaysSince1900 131 - 1); 132 int millisecondsInDay = 133 ( int ) ((date - Math.floor(date)) 134 * ( double ) DAY_MILLISECONDS + 0.5); 135 136 calendar.set(GregorianCalendar.MILLISECOND, millisecondsInDay); 137 return calendar.getTime(); 138 } 139 else 140 { 141 return null; 142 } 143 } 144 145 /** 146 * Given a double, checks if it is a valid Excel date. 147 * 148 * @return true if valid 149 * @param value the double value 150 */ 151 152 public static boolean isValidExcelDate(double value) 153 { 154 return (value > -Double.MIN_VALUE); 155 } 156 157 /** 158 * Given a Calendar, return the number of days since 1600/12/31. 159 * 160 * @return days number of days since 1600/12/31 161 * @param cal the Calendar 162 * @exception IllegalArgumentException if date is invalid 163 */ 164 165 private static int absoluteDay(Calendar cal) 166 { 167 return cal.get(Calendar.DAY_OF_YEAR) 168 + daysInPriorYears(cal.get(Calendar.YEAR)); 169 } 170 171 /** 172 * Return the number of days in prior years since 1601 173 * 174 * @return days number of days in years prior to yr. 175 * @param yr a year (1600 < yr < 4000) 176 * @exception IllegalArgumentException if year is outside of range. 177 */ 178 179 private static int daysInPriorYears(int yr) 180 { 181 if (yr < 1601) 182 { 183 throw new IllegalArgumentException( 184 "'year' must be 1601 or greater"); 185 } 186 int y = yr - 1601; 187 int days = 365 * y // days in prior years 188 + y / 4 // plus julian leap days in prior years 189 - y / 100 // minus prior century years 190 + y / 400; // plus years divisible by 400 191 192 return days; 193 } 194 195 // set HH:MM:SS fields of cal to 00:00:00:000 196 private static Calendar dayStart(final Calendar cal) 197 { 198 cal.get(Calendar 199 .HOUR_OF_DAY); // force recalculation of internal fields 200 cal.set(Calendar.HOUR_OF_DAY, 0); 201 cal.set(Calendar.MINUTE, 0); 202 cal.set(Calendar.SECOND, 0); 203 cal.set(Calendar.MILLISECOND, 0); 204 cal.get(Calendar 205 .HOUR_OF_DAY); // force recalculation of internal fields 206 return cal; 207 } 208 209 // --------------------------------------------------------------------------------------------------------- 210 } 211