Getting a tad off topic here (unless we consider all those military and naval men, and JA's Aunt, who went to the tropics) but it is very easy to tell the time when the day is practically twelve hours long all year round. I live between the Tropic of Capricorn and the Equator, and I am usually accurate to within a quarter of an hour when I estimate the time by the sun. This is quite accurate enough for an agricultural society.