Survex and dates

[Olly Betts]

On Wed, Jul 28, 2010 at 11:57:24AM +0100, Mark Shinwell wrote:
> On Wed, Jul 28, 2010 at 12:36:02PM +0200, Graham Mullan wrote:
> > Is it going to be possible to deal with the Unix date problem and get  
> > Survex to recognise dates earlier than 1970, or are we tied down by the  
> > vagaries of one operating system?
> 
> I'm not sure what you mean by the Unix date problem.  The usual practice is
> for the standard Unix time type (time_t) to be signed, so you can go back
> before the 1970 epoch.  A 32-bit time_t permits dates from 1901..2038 and the
> 64-bit version goes back older than any cave.

Yes, there's no "Unix date problem" here - the only "Unix date problem" I
am aware of is that signed 32-bit time_t wraps in 2038:

http://en.wikipedia.org/wiki/Year_2038_problem

Also, note that Microsoft Windows uses the 1970 epoch too:

http://msdn.microsoft.com/en-us/library/1f4c8f33%28VS.80%29.aspx

Currently the .3d format stores the date as seconds since 1970, and this
is documented as unsigned, though cavern currently rejects any dates
outside 1970-2038.  This is really just because I haven't had much feedback
on what ranges of dates are useful, and what granularity of time stamping
is useful, so it's just in the easiest format to store - that which we
get from the system.

So anyway, why not tell us what dates you actually want to be able to use?

Cheers,
    Olly