I worked at WCHE from 2003 till 2009 so perhaps I can shed some light on this. I don’t know if they have recently been granted a PSRA or a PSSA. When I was there, I think we tried to get them but we were denied, so the sign on/off times for December were 7:15AM and 4:45PM. I believe the reason they are called “approximate times” is because sunrise on the 1st of the month, and sunrise on the 30th of the month, can be quite different. I’m pretty sure the sign on/off times are derived from the middle of the month, such as the 15th day, and then rounded off to the nearest quarter hour.
It was impossible to do a morning show all year round from 7AM-10AM because during part of March, October and December we had to wait until 7:15AM to turn on the transmitter, and in January we had to wait until 7:30AM to turn it on. Also, the signal at that time was so weak that the topic of most callers was how they couldn’t hear us over WWKB. Eventually we moved the morning show to midday to avoid the poor reception.
Sunset. The daytimer’s arch enemy.