/*
*******************************************************************************
* Copyright (C) 2004-2008, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*
*/
package com.ibm.icu.dev.tool.timescale;
import java.util.Date;
import java.util.Locale;
import com.ibm.icu.text.MessageFormat;
import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.GregorianCalendar;
import com.ibm.icu.util.SimpleTimeZone;
import com.ibm.icu.util.TimeZone;
/**
* This tool calculates the numeric values of the epoch offsets
* used in UniversalTimeScale.
*
* @see com.ibm.icu.util.UniversalTimeScale
*/
public class EpochOffsets
{
/**
* The default constructor.
*/
public EpochOffsets()
{
}
private static final long ticks = 1;
private static final long microseconds = ticks * 10;
private static final long milliseconds = microseconds * 1000;
private static final long seconds = milliseconds * 1000;
private static final long minutes = seconds * 60;
private static final long hours = minutes * 60;
private static final long days = hours * 24;
// Java measures time in milliseconds, not in 100ns ticks.
private static final long javaDays = days / milliseconds;
private static int[][] epochDates = {
{ 1, Calendar.JANUARY, 1},
{1970, Calendar.JANUARY, 1},
{1601, Calendar.JANUARY, 1},
{1904, Calendar.JANUARY, 1},
{2001, Calendar.JANUARY, 1},
{1899, Calendar.DECEMBER, 31},
{1900, Calendar.MARCH, 1}
};
/**
* The <code>main()</code> method calculates the epoch offsets used by the
* <code>UniversalTimeScale</code> class.
*
* The calculations are done using an ICU <code>Calendar</code> object. The first step is
* to calculate the Universal Time Scale's epoch date. Then the epoch offsets are calculated
* by calculating each epoch date, subtracting the universal epoch date from it, and converting
* that value to ticks.
*
* @param args - the command line arguments.
*/
public static void main(String[] args)
{
TimeZone utc = new SimpleTimeZone(0, "UTC");
// Jitterbug 5211: .Net System.DateTime uses the proleptic calendar,
// while ICU by default uses the Julian calendar before 1582.
// Original code: Calendar cal = Calendar.getInstance(utc, Locale.ENGLISH);
// Use a proleptic Gregorian calendar for 0001AD and later by setting
// the Gregorian change date before 0001AD with a value
// that is safely before that date by any measure, i.e.,
// more than 719164 days before 1970.
long before0001AD = -1000000 * javaDays;
GregorianCalendar cal = new GregorianCalendar(utc, Locale.ENGLISH);
cal.setGregorianChange(new Date(before0001AD));
MessageFormat fmt = new MessageFormat("{0, date, full} {0, time, full} = {1}");
Object arguments[] = {cal, null};
System.out.println("Epoch offsets:");
// January 1, 0001 00:00:00 is the universal epoch date...
cal.set(1, Calendar.JANUARY, 1, 0, 0, 0);
long universalEpoch = cal.getTimeInMillis();
for (int i = 0; i < epochDates.length; i += 1) {
int[] date = epochDates[i];
cal.set(date[0], date[1], date[2]);
long millis = cal.getTimeInMillis();
arguments[1] = Long.toString((millis - universalEpoch) * milliseconds);
System.out.println(fmt.format(arguments));
}
}
}