i believe fedex typically says "deliver by 4:30pm", which doesn't provide any good information on when in the day they will come. given where i live in my town, fedex usually comes around 3pm so i leave work around 2pm to be safe. they sometimes come as late as 5:30pm depending on how busy their day is.
can you call your local fedex facility to get an estimate on when they are typically in your neighborhood?