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Serial date, Excel, Lotus, MJD, PolyForth

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Here's a question for the computer historians.

Who invented - or was the first to use - the serial date system based
on year 1900 ?

What's good about year 1900?  Well it means that for the epoch we're
most interested in, serial dates can be stored as a single 16-bit number
and the computer math required to manipulate them is easy.

Googling one finds this serial calendar referred to as the
"Excel Serial Day Number"
http://www.fourmilab.ch/documents/calendar/

Another Bill Gates' innovation?  Alas no.  Microsoft admits they
took it from Lotus 123 - a leading spreadsheet program of the day.
Oh, and yes, there was a bug in the Lotus implementation which has
faithfully been copied to this day - namely, the assumption that 1900
was a leap year!

So what's this got to do with Forth?  As it happens Forth Inc also had
a serial calendar based on year 1900 which they called MJD or
"Modified Julian Day".  Google "MJD" however, and one will find
it refers to an entirely different serial date system which predated
Forth Inc.  So how was it that Forth Inc came to call their system
"MJD" ?  Were they unaware the name and acronym had already been
taken?

Back to the question I posed at the beginning.  Who invented - or was
the first to implement - the 1900 serial date system?  Google it and
the earliest reference one will find is Lotus 123.  But Lotus was
released in 1983 and Forth Inc predated it.  So how did Forth Inc come
its serial calendar and when?

A final twist.  The programmer who wrote the first version of Lotus 123
was one Jonathan Sachs - the same Jonathan Sachs who implemented
STOIC, a variant of Forth, in the mid 1970's.

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Serial date, Excel, Lotus, MJD, PolyForth "Ed" <invalid@nospam.com> - 2013-05-09 12:40 +1000
  Re: Serial date, Excel, Lotus, MJD, PolyForth "Elizabeth D. Rather" <erather@forth.com> - 2013-05-08 20:04 -1000
    Re: Serial date, Excel, Lotus, MJD, PolyForth Mark Wills <forthfreak@gmail.com> - 2013-05-09 00:17 -0700
    Re: Serial date, Excel, Lotus, MJD, PolyForth "Elizabeth D. Rather" <erather@forth.com> - 2013-05-08 22:18 -1000
      Re: Serial date, Excel, Lotus, MJD, PolyForth "Ed" <invalid@nospam.com> - 2013-05-10 12:19 +1000
    Re: Serial date, Excel, Lotus, MJD, PolyForth Alex McDonald <blog@rivadpm.com> - 2013-05-09 06:37 -0700
    Re: Serial date, Excel, Lotus, MJD, PolyForth C G Montgomery <cgm@physics.utoledo.edu> - 2013-05-09 17:30 -0400
    Re: Serial date, Excel, Lotus, MJD, PolyForth "Ed" <invalid@nospam.com> - 2013-05-11 14:57 +1000
  Re: Serial date, Excel, Lotus, MJD, PolyForth "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-05-09 18:41 -0400

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