[Ads-l] Julian date

[victor steinbok]

I'm sure this message will be TMI for those who already know or don't care
about the technical details. But that's my mansplaining style. Please
forgive the garrulous exposé.

Odd jargon that I came across but haven't heard previously in this context.
Turns out, it's been in use at least since WWII. And it dates back 444
years, in principle, although not in execution.

OED does mention "Julian period" in the head note for "Julian", which, in
turn, identifies it with Scaliger Scale. I'll tie it all up in a minute
(OED note quoted below).

In 1582 (or thereabouts - OED has 1582, Wiki has 1583) Joseph Justus
Scaliger had proposed the "Julian Period", which comprised most (back then
- all) of the historical knowledge of the period. I don't want to go into
too much detail, but the main thrust is that "Julian" refers to Scaliger's
Julian Dating system, which is named after Scaliger's father, and not to
the Julian Calendar, which is named for his father's similarly-named more
famous predecessor.

I've known this system as Scaliger Scale since I was 8, but the head word
in Wikipedia is Julian Day - and that's how it's commonly referred to in
the respective academic/technological fields. The main uses are
astronomical, historical, military and software, although historians tend
to dismiss its usefulness these days (in my experience). There's no mention
in the OED as to what this dating system encompasses, which, I believe, is
an omission worth rectifying.

The system encompasses Julian Year - which is the number of years since 1
January 4713 BCE (4712 BC under Julian Calendar, which is a part of the
confusion) - and the Julian Day, which counts days continuously from that
same founding day (so, today is JD 2461259 or Scaliger 2461259). The OED
note skips all that detail:

"Julian period, a period of 7980 Julian years, proposed by Joseph Scaliger
in 1582 as a universal standard of comparison of chronology, consisting of
the product of the numbers of years in the solar and lunar cycles and the
cycle of the indiction (28 × 19 × 15)"

There's no distinction made in the OED entry between the two different
senses of Julian - pertaining to Julian Calendar (since modified as the
Gregorian Calendar) vs. pertaining to Scaliger Scale (served as an
inspiration for Star Trek star-date labeling).

And this is where my surprise comes in. Apparently, "Julian Date" has been
in use in manufacturing/retail since the 1940s (at least) to refer not to
Scaliger's JD number but to the number of days from 1 January of the
current year. There are several coding variations that incorporate the last
two or just the last digit of the year, but, for many perishables, just the
three-digit number is used for packaging date. You fill find this number on
packages of mushrooms, eggs, bagged lettuce and a few other things (e.g.,
Belgian beer) - unless a sell-by, best-by or expiration date is listed
instead (eggs include both).

The industry standard is "Julian Date" and not "Julian Date Code".

https://eggsafety.org/understanding-dates-egg-cartons/

VS-)

PS: If anyone wants to see an example, I have a photo of a Julian Date on a
Belgian beer label. Otherwise, refer to the link above.

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