I knew that over the course of human history, the calendar and time
'evaluations' were changed more than twice. What caught me off guard was
that strftime was treated with the same ambiance to julianday as being
+12hr from midnight when I thought I was asking for a midnight time value.
This is just one of those things that I'll need to keep in the back of my
mind when playing with this. Right now, my work project is dealing with
time differences with the resolution of minutes. The 12hour thing doesn't
affect me.
As a matter of fact, I started to work with doing my time deltas using
julianday, but, I ran into some float rounding issues and the math was
shorting me by at least a second, which made 1 hour look like 59 minutes.
Switched to strftime('%s',...) to do the math based on seconds and I've got
more than enough resolution for what I'm doing.
On Wed, Sep 27, 2017 at 10:01 PM, Simon Slavin <[email protected]> wrote:
>
>
> On 28 Sep 2017, at 2:51am, Keith Medcalf <[email protected]> wrote:
>
> >> I would have expected 0:00, not 12:00. Does this tie into julianday
> >> being a 12 hour offset?
> >
> > Six centuries or so ago it was "kind of difficult" to measure when the
> sun was "directly underfoot" at the prime meridian (0 deg, or Greenwich
> England, more or less) when your observation point was located on the prime
> meridian. It was pretty easy however to be able to tell when "noon" is
> (when the sun is at its maximum altitude) by an observer at the prime
> meridian. So the juliandate is measures a day from noon to noon.
>
> Yet humans still don’t like talking about the number zero. So it’s still
> called "twelve o’clock" by everyone except programmers. As is midnight.
>
> Simon.
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