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Date: Tue, 12 Feb 2002 18:55:56 +0900
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Thread-Topic: NTP time scale and UTC
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Subject: [FreeBSD-users-jp 66900] NTP time scale and UTC
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$B=;M'6bB0%7%9%F%`%=%j%e!<%7%g%s%:$NE*>l$G$9!%(J

SNTP$B$G(JNTP$B%5!<%P$+$i;~9o>pJs$r$b$i$C$F!$$H$"$k(JM$$B$N%^%7%s$N(J
$B%7%9%F%`;~9o$r%;%C%H$9$k%W%m%0%i%`$N:n@.$K4X78$7$F!$(J
NTP$B%5!<%P$,(JSNTP$B$G65$($F$/$l$k;~9o$NIC>pJs$N$3$H$GG:$s$G$$$^$9!%(J
$BFC$K!$(JNTP$B%5!<%P$,$/$l$kIC?t$r2r<a$9$k$H$-$K1<IC$r4^$s$@IC(J
$B$H2r<a$9$k$N$+4^$^$J$$IC$H2r<a$9$k$N$+$G$9!%(J

ntpd-4.1.71$B$KImB0$N%I%-%e%a%s%H(Jleap.htm$B$N!$(J
>Reckoning with NTP and UTC Leap seconds
>
>The NTP timescale is based on the UTC timescale, 
>but not necessarily always coincident with it. 
>At the first tick of the UTC Era, which began
>at 0h on 1 January 1972 (MJD 41,318.0) the NTP clock 
>read 2,272,060,800, representing the number of standard seconds 
>since the beginning of the NTP era at 0h on 1 January 1900
>(MJD 15,021.0) according to the Gregorian calendar. 
>The insertion of leap seconds in UTC and subsequently 
>into NTP does not affect the UTC or NTP oscillator frequency, 
>only the conversion between NTP network time and UTC civil time. 
>However, since the only institutional memory available to NTP are 
>the UTC broadcast services, the NTP timescale is in effect reset 
>to UTC as each broadcast timecode is received. 
>Thus, when a leap second is inserted in UTC and subsequently 
>in NTP, knowledge of all previous leap seconds is lost.

$B$r$I$&M}2r$9$l$P$h$$$N$+$,$o$+$C$F$*$j$^$;$s!%(J
$B<1<T$NJ}!$2r@b$$$?$@$1$^$;$s$G$7$g$&$+!)(J
$BFC$K(J"UTC broadcast services"$B$H$$$&$N$,!$(Jntp$B%W%m%H%3%k>e$N5!G=$J$N$+(J
$B$"$k$$$O(JGPS$B$^$?$O(JJJY$BEy$N;~Js$J$I$N$3$H$r;X$7$F$$$k$N$+$,(J
$BNI$/$o$+$C$F$$$^$;$s!%(J

$B$J$<G:$`$+$H?=$7$^$9$H!$(J
$B8=>u$G$O!$1<ICBP1~$K$7$?(JFreeBSD 4.2$B$N%^%7%s$G(J
ntpd 4.1.71-a $B$N(Jpackage$B$rF0$+$7$F2>$K(JNTP$B%5!<%P$H$7$F$*$j$^$9!%(J
Windows 2000$B$N%^%7%s>e$G(JTrueTime$B<R$N(JWinSync$B$H$$$&(J
$B;~9o@_DjMQ(JSNTP$B%/%i%$%"%s%H%W%m%0%i%`$rF0$+$9$H(J
FreeBSD$B%^%7%s>e$N(Jdate$B%3%^%s%I$GI=<($5$l$k$h$j$b(J
$BLs(J22$BICJ,?J$s$@;~9o$,I=<($5$l$^$9!%(J
$B$3$N:9$O!$(JFreeBSD$B>e$N(Jntpd$B$,1<IC$r4^$`IC>pJs$r(J
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$BM3Mh$9$k$H;W$$$^$9!%(J
$B$=$3$G!$K\Mh(JSNTP$B$GDLCN$5$l$kIC>pJs$O1<IC$r4^$`$N$+(J
$B4^$^$J$$$N$+$H$$$&$3$H$,M}2r$G$-$F$$$J$$$?$a$K$3$N$h$&$J(J
$B<ALd$H$J$j$^$7$?!%(J
$B$^$?!$:#!$D>@\%$%s%?!<%M%C%H>e$N8x3+(Jntp$B%5!<%P$+$i(J
$B<h$l$k4D6-$G%F%9%H$7$F$$$J$$$?$a!$$=$l$i$N%5!<%P$,$/$l$k(J
$BCM$,1<IC$r4^$`$N$+4^$^$J$$$N$+$,%A%'%C%/$G$-$F$$$J$$$3$H$r(J
$B$*CG$j?=$7>e$2$^$9!%(J
--
Bunpei Matoba
Manager
Products & Solutions Department
Products & Solutions Division
Sumitomo Metal System Solutions Co.,LTD.
Ichimatsu Building 4F
2-18, Ikenohata 1-Chome, Taitoh-ku
Tokyo, 110-0008 JAPAN
Phone: +81-3-5815-7278

