Before someone else asks, here's a source to confirm 23: http://maia.usno.navy.mil/ser7/tai-utc.dat
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 33 as of 2006 - 10 as of 1972 = 23 total And there will be another one next year: 2009 JAN 1 =JD 2454832.5 TAI-UTC= 34.0 S + (MJD - 41317.) X 0.0 S On Thu, Jul 3, 2008 at 3:00 AM, Monty, James T <[EMAIL PROTECTED]> wrote: > There's a good article about computerized timekeeping in the current > issue of Government Computer News: > > http://www.gcn.com/print/27_15/46509-1.html > > Who's got the time? > As computer systems become increasingly precise, a conflict emerges > between human and machine measurements > By Joab Jackson > > To explain epoch time, Mr. Jackson writes: > > For Posix-based computers such as Unix or Linux, time began Jan, 1, > 1970, at midnight. The time according to those machines is the > number of seconds that have accumulated since. For instance, the > Greenwich Mean Time 8:22 p.m., Tuesday, June 10, 2008, translates to > 1213129345 in Posix-speak. > > Naturally, I fired up DateTime to verify this value: > > C:\>perl -MDateTime -le "$dt = DateTime->new( year => 2008, month => > 6, day => 10, hour => 20, minute => 22 ); print $dt->epoch()" > 1213129320 > > C:\> > > Hmm...off by 25 seconds. When I factor out DateTime, I get the same > result: > > C:\>perl -MTime::Local -le "print timegm(0,22,20,10,5,2008)" > 1213129320 > > C:\>perl -MPOSIX -le "print POSIX::strftime(q{%Y-%m-%dT%H:%M:%S}, > gmtime(1213129345))" > 2008-06-10T20:22:25 > > C:\>perl -MPOSIX -le "print POSIX::strftime(q{%Y-%m-%dT%H:%M:%S}, > gmtime(1213129320))" > 2008-06-10T20:22:00 > > C:\> > > There had been 23 leap seconds as of June 10, not 25, so this doesn't > account for the difference exactly: > > C:\>perl -MDateTime -le "$dt = DateTime->new( year => 2008, month => > 6, day => 10, hour => 20, minute => 22, time_zone => 'UTC' ); print > $dt->leap_seconds()" > 23 > > C:\> > > I've written the author to thank him for his excellent article and to > ask him how he computed the value 1213129345. > > -- > Jim Monty > > <html> > <body> > <p>***********************************************************************</p> > <p>The information in this email is confidential and may be legally > privileged. > It is intended solely for the addressee. Access to this email by anyone else > is > unauthorized. If you are not the intended recipient, any disclosure, copying, > distribution or any action taken or omitted to be taken in reliance on it, is > prohibited and may be unlawful. When addressed to our clients any opinions or > advice contained in this email are subject to the terms and conditions > expressed in the governing KPMG client engagement letter.</p> > <p>***********************************************************************</p> > </body> > </html> > > -- Matthew O. Persico
