[tz] Dealing with Pre-1970 Data
David Patte ₯
dpatte at relativedata.com
Sun Sep 1 13:03:48 UTC 2013
On 2013-09-01 6:35, Zefram wrote:
>> However the one I was really thinking about was the 'equation of
>> >time' calculation in a format we can use as a 'standard'.
Equation of time calculations are non-trivial requiring the knowledge of
the variations of the orbit of the earth (to calculate sun position), as
well as variations in earth revolution speed (to calculate DeltaT). For
accuracy, astronomical software often uses large tables and series of
thousands of polynomials to estimate local apparent time in the past.
This is clearly outside the scope of a tz database.
There are simplifications to these formulas, but they are only accurate
for short timeframes.
More information about the tz