Look in the sample folder that was most likely installed when you installed RS5000. There is a DayOfWeek.ACD sample in there.
It's in Projects/Samples/ENU/v20/Rockwell Automation on my machine.
HTH
I think I was incorrect. If you look at the GSV WALLCLOCKTIME object it doesn't appear that there is a day of week value, just day of month (and others).