org.vishia.util

Class LeapSeconds

java.lang.Object

org.vishia.util.LeapSeconds

public class LeapSeconds
extends java.lang.Object

This class supports the handling with Leap seconds.
Background:

• UTC (= Coordinated Universal Time ) follows the caesium atomic clock, but it is coordinated with the earth rotation. respectively it follows the simple division of 1 year into 365 * 24* 3600 seconds and 366 * 24 * 3600 seconds in a leap year. If leap seconds are occurred, the second count of UTC is the same for 2 seconds.
• In computer systems, often UTC is used, because the unix-time also count simple seconds without regarding of leap seconds. Therefore, also the class java.util.Date based on UTC.
• The TAI (= en.wikipedia.org/wiki/International_Atomic_Time counts uniformly continuous and faster than the earth rotation. Thats why leap seconds are necessary to adapt the earth-rotation oriented second count (to UTC).
• The time from GPS positioning follows the TAI, with a constant difference of 19 seconds, without any leap seconds. Why 19 seconds? It's historical.
• In technical systems a strict uniformly continuous time counter is better to than the UTC.

This class helps to adapt GPS or other strict uniformly continuous time counter to UTC and to java.util.Date. A table of leap seconds may be given outside, because there are not defined yet for the future.

Field Summary

Fields

Modifier and Type	Field and Description
protected int[]	leapSeconds Array of number of leap seconds.
protected long[]	millisecondsGPSForLeapSeconds Array of values of seconds after 1970, which are leap seconds.
protected long[]	millisecondsUTCForLeapSeconds Array of values of seconds after 1970, which are UTC seconds.
protected static LeapSeconds	singleton All methods are static, but uses internally data of this class.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	LeapSeconds()

Method Summary

Modifier and Type	Method and Description
static java.util.Date	dateFromGPS(long millisecondsGPS) Returns a Date object from given GPS-seconds.
protected void	initFix() initializes the table of leap seconds with fix dates.
static long	millisecondsGPSfromUTC(long millisecondsUTC)
static int	secondsGPSfromUTC(int secondsUTC_1970)
static void	setLeapSeconds(int idx, java.util.Date date) Sets the leap seconds for a given timestamp.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

singleton

protected static LeapSeconds singleton

All methods are static, but uses internally data of this class. Therefore an singleton instance is created if not exist and referenced here.

leapSeconds

protected final int[] leapSeconds

Array of number of leap seconds. @java2c=simpleArray.

millisecondsUTCForLeapSeconds

protected long[] millisecondsUTCForLeapSeconds

Array of values of seconds after 1970, which are UTC seconds. The value of seconds doesn't count leaps seconds. @java2c=simpleArray.

millisecondsGPSForLeapSeconds

protected long[] millisecondsGPSForLeapSeconds

Array of values of seconds after 1970, which are leap seconds. The value of seconds counts also leaps seconds (not UTC, but GPS). @java2c=simpleArray.

Constructor Detail

LeapSeconds

protected LeapSeconds()

Method Detail

setLeapSeconds

public static void setLeapSeconds(int idx,
                                  java.util.Date date)

Sets the leap seconds for a given timestamp. This routine should be called on startup phase if a input is available.

Parameters:

index - number of leap seconds for this date. It is the index in the table.

date - The UTC timestamp after which a leap second is inserted.

initFix

protected void initFix()

initializes the table of leap seconds with fix dates. The dates are get from http://en.wikipedia.org/wiki/Leap_second Dates after 2008 are guessed.

dateFromGPS

public static java.util.Date dateFromGPS(long millisecondsGPS)

Returns a Date object from given GPS-seconds.

Parameters:

millisecondsGPS - Value of milliseconds from Jan-1-1970, which counts also leap seconds.

Returns:

The Date-Object is UTC-oriented. Exactly in a leap seconds the same value is returned as in second before.

millisecondsGPSfromUTC

public static long millisecondsGPSfromUTC(long millisecondsUTC)

secondsGPSfromUTC

public static int secondsGPSfromUTC(int secondsUTC_1970)