Re: Concalendrical reference point

Andreas Johansson writes:
 > Tim May wrote:
 > >Note that this thread is of marginal topicality, but I can't think of
 > >a better place to ask.
 > >
 > >I've been trying to develop a calendar.  It's just a standard calendar
 > >for use on Earth, with no speacal concultural associations.  I'm
 > >fairly happy with the mechanics of the thing, but one question
 > >troubles me - from what date to start the long count of years?  I
 > >could just start it from when I finish the calendar (or that year,
 > >anyway - I'm thinking of having the year start at the vernal equinox,
 > >like the Vorlin calendar) but that seems to perhaps attach too much
 > >importance to the creation of the calendar itself.  I'm unable to
 > >decide on any one event of such importance in history.  So one idea I
 > >had was to simply take the earliest recorded event which can be
 > >precisely dated (at least to the year) with a reasonable degree of
 > >certainty. So my question is, does anyone know what that event is?
 > >(Preferably not an astronomical observation, as we only know these
 > >with accuracy because we can project them back in time, and could do
 > >this in theory regardless of contemporary records - but another event
 > >recorded with reference to an astronomical event would be fine.)
 >
 > A battle between the Lydians and the Medes that took place on the 28th of
 > May 585 BC is at least a good contender - it was interupted by a total solar
 > eclipse. Seen it mentioned as "earliest reliably dated historical event" in
 > a couple different books.
 >
 >                                                 Andreas

Good, good, this is the kind of thing I was looking for.  Now, another
question I should have asked - how do BC dates work?  That is, with
regard to the Julian/Gregorian shift?

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