This document calculates, for latitudes between 65 degrees
North and 65 degrees South and any date in the latter half of
the 20th century, the times of sunrise, sunset, and civil,
nautical, and astronomical twilight. The calculated times refer to
locations with a clear horizon and a standard refraction
correction for normal meteorological conditions. The calculated
times are accurate to within 2 minutes; higher accuracy is
seldom justified since local meteorological conditions will cause
the actual time to vary.