To calculate local sun (TT) time, use the following simple formula:
TT = GMT + LC + EOT,
where GMT - mean sun time on 0 meridian, where Greenwich observatory is situated.
It is a base time for zonal time shifts.
LC - longitude correction is geographical longitude expressed in time value, assuming
that 15° equals one mean hour. East longitude is positive, while west is negative.
EOT - equation of time expresses annual discrepancy between mean and true sun time.
It changes within ± 15 minutes.
In fact we deal with good approximation, because we can not take into account all
pecularities of Earth's movement. You can find EOT value in sun ephemeris window.
