How many seconds are in a day?
Day
The Jewish day begins at either sunset or nightfall (when three second-magnitude stars appear). The "Damascus Document", copies of which were also found among the Dead Sea scrolls, states regarding the observance of the Sabbath that "No one is to do any work on Friday from the moment that the Sun's disk stands distant from the horizon by the length of its own diameter," presumably indicating that the monastic community responsible for producing this work counted the day as ending shortly before the Sun had begun to set.