In M, the current date and time is contained in a special system variable,
$H (for "HOROLOG"). The format is a pair of integers separated by a comma,
e.g. "54321,12345" The first number is the number of days since December
31st, 1840, i.e. day number 1 is January 1st, 1841; the second is the number
of seconds since midnight.
But why 1841? According to Steve Clay, firstname.lastname@example.org, the following
answer appeared in the "Just Ask!" column of the September 1993 issue of
"M Computing," a publication of the M Technology Association, Silver Spring,
MD 20903 (Phone: 301-431-4070), in the form of a letter from James M.
"When I decided on specifications for the date routine, I remembered reading
of the oldest (one of the oldest?) U.S. citizen, a Civil War veteran, who
was 121 years old at the time. Since I wanted to be able to represent dates
in a Julian-type form so that age could be easily calculated and to be able
to represent any birth date in the numeric range selected, I decided that a
starting date in the early 1840s would be 'safe.' Since my algorithm worked
most logically when every fourth year was a leap year, the first year was
taken as 1841. The zero point was then December 30, 1840...
"That's the origin of December 31, 1840 or January 1, 1841. I wasn't party
to the MDC negotiations, but I did explain the logic of my choice to members
of the Committee."