Subject: Re: [lojban] Rafsi in cmene: way off track

From: [email-masked]
Date: Sun, 8 Jul 2001 20:50:54 EDT

Since we are talking about dates and the like, I'd like to say a few words 
about Julian. Calendars are a mess; of the hundred or so that have enjoyed 
some prominence somewhere somewhen, half a dozen are still in common use and 
translating among them is harder than figuring out the time in Delhi. Due to 
some quirks Mesopotamian mythology, all the survivors pretty much agree that 
a year has about 12 months, but they differ on the relation between months 
and moons, as well as how long a month is, when a month starts, when a year 
starts, what to do when the calendar gets out of synch with the heavens and 
what counts as out of synch. Calculating the time between to dates on any of 
these is a pain as well. Of course, there are cute little programs for doing 
this -- and translating between claendars as well (including some no one uses 
any more, like the Mayan?). Such programs use Julian dates for the various 
calendar dates, as do astronomers everywhere. A Julian date consists of the 
number of full dates and the fraction since 12 noon GMT on January 1, -4713 
(a quirk of a different mythology). So, at the moment it is 2452099.52 and 
rapidly changing further fractions, corresponding to July 8, 2001, 19:32 CDT. 
And this time is 1) the same everywhere in the world, 2) given in a single 
system, not varying through bases 28,29, 30 or 31, 12, 10, 24, 60, 60, maybe 
7, and take your pick -- in Julian precision is indefinitely extendable. 3) 
the system starts at 0 (the heretofore mentioned New Year's Day at noon), so 
all those muddles go.

Of course, there are some down sides. The date looks long, although it 
contains fewer characters than a standard civil date: 07/08/01 -- but / looks 
short. And the time side is inconvenient (unless everyone used it), since 
(as is so often in time measurements) nothing correlates very well with 
hours, minutes and seconds. An hour is .041[6 of a day, so a minute is 
.00069[4 and a second .0000115[740. And, of course, there is no regular 
coordination between day numbers and natural phenomena, days of the week or 
whatever else might be important to farmers, mechants, priests, etc. etc. On 
the other hand, periodic astronomical events recur in regular ways, since 
they are at the base of the system. 
Hey! Captain's log: Star date---.