I did an article for The Gettysburg Magazine years ago that dealt with this topic. Standard time zones were not adopted in the U.S. until 1883. Before then, the sun's passage over the local meridian established high noon in every town in the country. A Texan comparing watches with his opponent from Maine would have noticed a difference of about one hour and forty five minutes, owing to the longitude separation (26 degrees). That's just one reason why no two participants in a battle seem to agree on the timing of events. However, for a specific location and specific date in history, programs can determine the time of sunrise, sunset, moonrise, moonset, and the moon's azimuth/elevation in the sky, which helps somewhat.