Leap second

[Jozef Drahovsky]

Ahoj
zalezi od ucelu pouzitia, ak potrebujes vypocitat presny pocet sekund 
medzi nejakym datumom, tak to je vo FreeBSD ale aj inych SW problem, 
lebo funkcie casu ignoruju leap sekundy a dostanes skreslene vysledky.
Pre bezny zivot to nevadi, ale astronomovia a fyzici s tym maju vazny 
problem. Led sa prihodil leap sekunda tak druzice na sekundu nezastanu, 
ale letia dalej.

Samotne FreeBSD cez NTP protokol akceptuje aj leap skundy a zapisuje ich 
do logov, takze zo systemoveho hladiska problem nie je.
Lenze obcas je problem ked mas v logu cas 23:59:60 alebo 23:59:61 co 
sposobi zrutenie niektorych software, ale to je neznalost programatorov.
Ten isty problem maju dochadzkove a mzdove systemy ked sa meni letny cas 
na zimy a ked nejaky pracovnik v ten den odpracoval dvadsatstvorku a to 
bolo  25 hodin.

Dnes mame difereciu 35 leap second medzi UTC a TAI a nejakych 16 leap 
sekund medzi UTC a GPS
Pozor na GPS lebo to ma dva casy jeden je presny z hodin vo vesmire bez 
leap sekund od 6.1.1980 a druhy je korigovany pre obcianske pouzitie s 
leap sekundami.

Male upozornenie: fyzici a astromomovia maju iny cas aj na naramkovych 
hodinkach a neviedia sa dohodnut, ktory je ten spravny :)

A este pridavam tabulu pre manualne prepocty s leap sekundami

  1961 JAN  1 =JD 2437300.5  TAI-UTC=   1.4228180 S + (MJD - 37300.) X 0.001296 S
  1961 AUG  1 =JD 2437512.5  TAI-UTC=   1.3728180 S + (MJD - 37300.) X 0.001296 S
  1962 JAN  1 =JD 2437665.5  TAI-UTC=   1.8458580 S + (MJD - 37665.) X 0.0011232S
  1963 NOV  1 =JD 2438334.5  TAI-UTC=   1.9458580 S + (MJD - 37665.) X 0.0011232S
  1964 JAN  1 =JD 2438395.5  TAI-UTC=   3.2401300 S + (MJD - 38761.) X 0.001296 S
  1964 APR  1 =JD 2438486.5  TAI-UTC=   3.3401300 S + (MJD - 38761.) X 0.001296 S
  1964 SEP  1 =JD 2438639.5  TAI-UTC=   3.4401300 S + (MJD - 38761.) X 0.001296 S
  1965 JAN  1 =JD 2438761.5  TAI-UTC=   3.5401300 S + (MJD - 38761.) X 0.001296 S
  1965 MAR  1 =JD 2438820.5  TAI-UTC=   3.6401300 S + (MJD - 38761.) X 0.001296 S
  1965 JUL  1 =JD 2438942.5  TAI-UTC=   3.7401300 S + (MJD - 38761.) X 0.001296 S
  1965 SEP  1 =JD 2439004.5  TAI-UTC=   3.8401300 S + (MJD - 38761.) X 0.001296 S
  1966 JAN  1 =JD 2439126.5  TAI-UTC=   4.3131700 S + (MJD - 39126.) X 0.002592 S
  1968 FEB  1 =JD 2439887.5  TAI-UTC=   4.2131700 S + (MJD - 39126.) X 0.002592 S
  1972 JAN  1 =JD 2441317.5  TAI-UTC=  10.0       S + (MJD - 41317.) X 0.0      S
  1972 JUL  1 =JD 2441499.5  TAI-UTC=  11.0       S + (MJD - 41317.) X 0.0      S
  1973 JAN  1 =JD 2441683.5  TAI-UTC=  12.0       S + (MJD - 41317.) X 0.0      S
  1974 JAN  1 =JD 2442048.5  TAI-UTC=  13.0       S + (MJD - 41317.) X 0.0      S
  1975 JAN  1 =JD 2442413.5  TAI-UTC=  14.0       S + (MJD - 41317.) X 0.0      S
  1976 JAN  1 =JD 2442778.5  TAI-UTC=  15.0       S + (MJD - 41317.) X 0.0      S
  1977 JAN  1 =JD 2443144.5  TAI-UTC=  16.0       S + (MJD - 41317.) X 0.0      S
  1978 JAN  1 =JD 2443509.5  TAI-UTC=  17.0       S + (MJD - 41317.) X 0.0      S
  1979 JAN  1 =JD 2443874.5  TAI-UTC=  18.0       S + (MJD - 41317.) X 0.0      S
  1980 JAN  1 =JD 2444239.5  TAI-UTC=  19.0       S + (MJD - 41317.) X 0.0      S
  1981 JUL  1 =JD 2444786.5  TAI-UTC=  20.0       S + (MJD - 41317.) X 0.0      S
  1982 JUL  1 =JD 2445151.5  TAI-UTC=  21.0       S + (MJD - 41317.) X 0.0      S
  1983 JUL  1 =JD 2445516.5  TAI-UTC=  22.0       S + (MJD - 41317.) X 0.0      S
  1985 JUL  1 =JD 2446247.5  TAI-UTC=  23.0       S + (MJD - 41317.) X 0.0      S
  1988 JAN  1 =JD 2447161.5  TAI-UTC=  24.0       S + (MJD - 41317.) X 0.0      S
  1990 JAN  1 =JD 2447892.5  TAI-UTC=  25.0       S + (MJD - 41317.) X 0.0      S
  1991 JAN  1 =JD 2448257.5  TAI-UTC=  26.0       S + (MJD - 41317.) X 0.0      S
  1992 JUL  1 =JD 2448804.5  TAI-UTC=  27.0       S + (MJD - 41317.) X 0.0      S
  1993 JUL  1 =JD 2449169.5  TAI-UTC=  28.0       S + (MJD - 41317.) X 0.0      S
  1994 JUL  1 =JD 2449534.5  TAI-UTC=  29.0       S + (MJD - 41317.) X 0.0      S
  1996 JAN  1 =JD 2450083.5  TAI-UTC=  30.0       S + (MJD - 41317.) X 0.0      S
  1997 JUL  1 =JD 2450630.5  TAI-UTC=  31.0       S + (MJD - 41317.) X 0.0      S
  1999 JAN  1 =JD 2451179.5  TAI-UTC=  32.0       S + (MJD - 41317.) X 0.0      S
  2006 JAN  1 =JD 2453736.5  TAI-UTC=  33.0       S + (MJD - 41317.) X 0.0      S
  2009 JAN  1 =JD 2454832.5  TAI-UTC=  34.0       S + (MJD - 41317.) X 0.0      S
  2012 JUL  1 =JD 2456109.5  TAI-UTC=  35.0       S + (MJD - 41317.) X 0.0      S
  2015 JUL  1 =JD 2457204.5  TAI-UTC=  36.0       S + (MJD - 41317.) X 0.0      S

Jozef


Dňa 7. 6. 2015 o 21:26 Jan Dušátko napísal(a):
> Ahoj
> shanim nejake informace o problemu s leap second (30.6.2015 23:59:59)
> Veskere dostupne informace tvrdi, ze FreeBSD s uvedenym nema problem,
> ale nenasel jsem rozumne vysvetleni proc.
>
> Vite nekdo neco blizsiho ?
>
> Honza