DavidKaye said:Interesting that KWUN 1480 in Concord used to have slightly different signoffs. In January it was 5:00, November 5:15. Since they had PSA I don't know what the corresponding sunrise times were.
Well a 10-mile difference in location (especially if it's a move to the east or west. as this one is) can easily affect some months' sign-on or sign-off time by 15 minutes. Remember, if the "average" time rounded to the nearest quarter hour is just over the imaginary dividing line (between, say, 5:00PM and 5:15PM), all it takes to move the sign-on or sign-off time by 15 minutes is a one-second change in the average. That's why stations that have separate day and night sites, which are sometimes just a few miles apart, have the times when they switch from day to night or night to day operation calculated separately. Had the FCC not handled the calculations that way, some of those stations could have been forced to sign off one site and then go silent for 15 minutes before being allowed to sign on the other site.