dateutil.java

java 调用windows的api

/*
 * DateUtil.java -
 *
 * This file is part of the Jawin Project: http://jawinproject.sourceforge.net/
 * 
 * Please consult the LICENSE file in the project root directory,
 * or at the project site before using this software.
 */

/* $Id: DateUtil.java,v 1.3 2004/06/14 19:35:13 arosii_moa Exp $ */

package org.jawin.io;

import java.util.Calendar;
import java.util.Date;

/**
 * Marshalling utility methods for handling the platform impedance between
 * dates in Win32 and Java.
 * <ul>
 * 	<li>Win32: 0 is Dec 30 1899</li>
 * 	<li>Java: 0 is Jan 1 1970</li>
 * </ul> 
 *
 * @version     $Revision: 1.3 $
 * @author      Stuart Halloway, http://www.relevancellc.com/halloway/weblog/
 */
public class DateUtil {

	/**
	 * private constructor to avoid instantiation, as this class only contains
	 * static methods.
	 */
	private DateUtil() {
		// never called
	}

	private static final int MILLISECONDS_IN_DAY = 1000 * 60 * 60 * 24;

	//Dec 30 1899 is 0 in Win32 date
	//Jan 1 1970 is 0 in Java date
	//difference between the two is 70 years + 2 days 
	//leap years are 1904, 1908, etc. = 17 leaps
	//(365 * 70) + 17 + 2
	private static final int SUN_MINUS_MICROSOFT = 25569;

	/**
	 * @return the java milliseconds since 1970 from a win32 date.
	 */
	public static long getJavaDate(double date) {
		double javaNormalizedDate = date - SUN_MINUS_MICROSOFT;
		long millis = Math.round(86400000L * javaNormalizedDate);
		Calendar cal = Calendar.getInstance();
		cal.setTime(new Date(millis));
		return millis - cal.get(Calendar.ZONE_OFFSET) - cal.get(Calendar.DST_OFFSET);
	}

	/**
	 * @return the win32 date from a java.lang.Date.
	 */
	public static double getWin32Date(java.util.Date dt) {
		return getWin32Date(dt.getTime());
	}

	/**
	 * @return the win32 date from a java milliseconds since 1970.
	 */
	public static double getWin32Date(long dt) {
		Date date = new Date(dt);
		Calendar cal = Calendar.getInstance();
		cal.setTime(date);
		long millis = date.getTime()
				+ cal.get(Calendar.ZONE_OFFSET)
				+ cal.get(Calendar.DST_OFFSET);
		return (double) millis / MILLISECONDS_IN_DAY + SUN_MINUS_MICROSOFT;
	}

}