Sept. 1, 2013
1:03 p.m.
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. --