I know you are supposed to fly it during the day and take it down at sunset. That's generally the rules for displaying the US flag.
Who knows the proper way to display the US flag on Memorial Day?
I looked it up and found this. "On Memorial Day the flag should be flown at half-staff from sunrise until noon only, then raised briskly to the top of the staff until sunset, in honor of the nation's battle heroes."
http://www.va.gov/opa/publications/celebrate/halfstaff.pdf
I hadn't known that Gator. Great question! Our vets deserve to be honored properly.
You're supposed to display the flag at half staff or half mast or something similar to that because someone has died and you're acknowledging their brave sacrifice and military service.