Some time limits should be applied when searching for daylight DX in the AM broadcast band. In my experiments, 2.5 hours is about as close as you can get to sunrise and sunset times before the band starts to change dramatically. The sun is setting here currently at 5:43 PM. I find that by 3:30PM the characteristics of the band have shifted somewhat toward longer range DX as late afternoon approaches. Morning sunrise here is 6:42 AM, and by 9:30 AM we are back to daytime conditions again. So, for purposes of tallying daytime DX on the AM band, and adding in an extra 30 minutes for safety padding, 3 hours after sunrise and 3 hours before sunset will be the start and stop limits for my DX tests.
Several stations have been received during daylight hours in excess of 500 miles. Stay tuned.