Reply To: Shaos Zemanios

If they could accurately measure time then I have a follow up question. R’ Eliezer gives simanim for the three periods of night. The Gemara asks whether the simanim are for the beginning of the periods or the end of the periods. If it’s for the beginning, we don’t need a siman for the first one because we know that it’s when the night starts. If it’s for the end then we don’t need a siman for the last one because we know that it’s when the morning starts. The Gemara answers that the simanim were for the end of the first, the beginning of the last, and the middle of the middle. If there was an accurate way to tell time, we wouldn’t need a siman for the middle of the middle because it’s exactly halfway between the beginning of the first and the end of the second.