I just ran across an interesting piece of trivia: The origin of November
17, 1858 (the beginning of time as we know it). Firebird uses it
because Interbase used it. Interbase used it because VMS used it. The
original VMS doc set claimed that November 17, 1858 was when the US
Naval Observatory export the photographic plate that because the basis
for modern time. In fact, however, VMS took it from TOP-20. TOP-20, in
turn, was called Tenex before DEC brought it from BBN (the same guys who
brought us the ArpaNet and Internet and the only company that couldn't
figure out how to make money from either). The original Tenex manual,
however, claimed that November 17, 1858 was the date that the Royal
Observatory at Greenwich exposed the photographic plate that established
the modern time standard.

It appears that he correct answer is more mundane. The Smithsonian
Observatory got into the satellite tracking business shortly after man
(or the Russians) started launching satellites. To make best use of
their IBM 704, they needed a base date. The 704 had 36 bit words but
only 18 bit index registers with instructions to load and save the index
registers from either half of the word (which was the basis for the
intergalactically famous Lisp operators CAR and CDR). The Smithsonian
guys decided to use the ancient Julian date system, which an origin of
January 1, 4713 B.C. That had more range than they had bits, so they
arbitrarily truncated the Julian date to 18 bits, giving an artificial
origin of November 17, 1858. QED

References:

http://www.ucolick.org/~sla/leapsecs/timescales.html
http://vms.tuwien.ac.at/info/humour/vms-base-time-origin.txt
http://parris.josh.com.au/humour/work/17Nov1858.shtml

--

Jim Starkey
Netfrastructure, Inc.
978 526-1376