Dates

[Olly Betts]

I'm in the process of adding date storage to Survex, and I'm wondering
how other cave surveying software typically represent dates?

What I've seen so far suggests that most software opts for the day,
month, and year (and so implicitly is limited to 1AD onwards).  That's
unlikely to be a problem with the date of a survey, but it's not much
use for date tagging of archeological data - a carbon dated find could
be over 30000 years old.  I doubt you'd want day or month for dates that
long ago, but a unified date scheme of some sort seems worth at least
investigating.

Does cave surveying software take into account the calendars in use at
the time, or is this just ignored?  It's relevant for date validation
(for example, September 3rd - September 13th 1752 didn't exist for the
UK or what's now the USA) and for correctly computing the length of date
spans.

The switch from the Julian to Gregorian calendar happened at different
times in different countries between 1582 (France, Spain, Portugal, and
Italy) and 1918 (Russia), and the difference grew in that time from 10
to 13 days.  I wouldn't be suprised if survey data exists from before
1918.  I've certainly seen drawn up surveys older than that.

Cheers,
    Olly