Calendar calculations

I want to do some calendar (and astronomical) calculations going back
roughly 2008 years.

First of all:

1. Yes, I know this year was picked in the middle ages, not at that
time.
2. Yes, I know Jesus was not really born that year.
3. Yes, I know it started with Year 1, not Year 0.
4. I'm vaguely aware of the complications in going from Julian to
Gregorian,
esp. when not all countries did it together.
5. Yes, I'm aware of our 4-100-400 rules for modern leap years.

So... how does our calendar define early dates? Do the leap years go
backwards? Do the Julian and Gregorian calendars agree on January 1,
Year 1?

Specifically, if I want to calculate the number of days since 1/1/1,
how
would I do it?

And to throw some more astronomy into the mix, how can I find the
nearest
Martian (northern) vernal equinox to 1/1/1?

Email me and/or post here as you wish...

Thanks,
Hal
.

Relevant Pages

  • [sci.astro] Time (Astronomy Frequently Asked Questions) (3/9)
    ... As such its content ranges from the Earth to the farthest ... There is also a calendar FAQ maintained by Claus Tondering ... strict sense obsolete, though often used (although not in astronomy, ... Subject: C.07 Easter: ...
    (sci.answers)
  • [sci.astro] Time (Astronomy Frequently Asked Questions) (3/9)
    ... As such its content ranges from the Earth to the farthest ... There is also a calendar FAQ maintained by Claus Tondering ... strict sense obsolete, though often used (although not in astronomy, ... Subject: C.07 Easter: ...
    (sci.astro)
  • Re: Octagon Earthworks alignment with moon likely is no accident
    ... basically the same calendar and that is handy. ... could prove axial rotation using the return of a star to a location - ... That is the cutoff point between the careful work of the great ... as astronomy and by association archaeology,at least in these matters. ...
    (sci.archaeology)
  • Re: Octagon Earthworks alignment with moon likely is no accident
    ... basically the same calendar and that is handy. ... celestial sphere observers who now treat astronomy as little more than ... as astronomy and by association archaeology,at least in these matters. ... the criminal forgetting of atl-atl technology. ...
    (sci.archaeology)
  • Re: Octagon Earthworks alignment with moon likely is no accident
    ... basically the same calendar and that is handy. ... celestial sphere observers who now treat astronomy as little more than ... as astronomy and by association archaeology,at least in these matters. ... ancient of our species. ...
    (sci.archaeology)