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Thread-Topic: Historical change of UNIX Epoch
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Subject: [FreeBSD-users-jp 66558] Historical change of UNIX Epoch
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$B=;M'6bB0%7%9%F%`%=%j%e!<%7%g%s%:$NE*>l$G$9!%(J

$B$I$&$G$b$$$$$h$&$J<ALd$G62=L$G$9!%(J
UNIX$BGn<12H$NJ}$KEP>l4j$($k$H9,$$$G$9!%(J

$B8=:_$N(J
FreeBSD Library Functions Manual
TIME(3)$B$K$O!$(J
>The time() function returns the value of time in seconds since 0 hours,
0
>minutes, 0 seconds, January 1, 1970, Coordinated Universal Time.
$B$H5-:\$5$l$F$$$^$9!%(J
$B$3$N$$$o$f$k(JUNIX Epoch$B$,!$(JGMT$B$G$O$J$/$F(JUTC$B$r$b$C$FDj5A$5$l$?$N$O!$(J
UNIX$B$NNr;K$NCf$N$$$D$N$3$m$+$i$J$N$G$7$g$&$+!)(J

http://cm.bell-labs.com/cm/cs/who/dmr/1stEdman.html
$B$K$h$k$H0J2<$N$h$&$K!$(J1973$BG/$+$i(Jclassical Unix epoch$B$,!$(J
$B$H$"$k$N$G$9$,!$$3$l$,(JUTC$B$H5-:\$5$l$F$$$?$N$+5$$K$J$j$^$7$F!%(J

We even anticipated the millenium bug: time was measured 
in sixtieths of a second since 1 Jan. 1971 as a 32 bit quantity. 
The BUGS section for time(II) remarks, "The cronological-minded 
reader will note that 2**32 sixtieths of a second is only about 2.5
years." 
Later, this was patched more than once by declaring a new epoch, 
then again in 1973 by making the units full seconds dating from 
the 1970 New Year--this is the "classical" Unix epoch. 
Of course, it only pushed the issue off to 2038. 
Yet, the cal program even in 1971 knew about the hanky-panky in 1752!. 
--
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

