I recently visited several cemeteries as part of my annual trek to MC & western ND on Memorial weekend. Some of the cemeteries had the veterans graves flags on them as early as Friday while some were getting put on Saturday and I was told by others that they would be put on Memorial Day morning. A discussion arose when they should be put on the graves. Some thought they should be put on the vets graves before the Memorial weekend as a lot of people like myself visit before the actual Memorial Day. Another was that the flag cannot be displayed in the dark so should not be put on the graves until sunup and taken down at sundown that same day. In MC they were and as far as I can remember at least on Saturday and this year on Friday. Does anyone know the know the proper etiquette for this situation?

From http://www.ushistory.org/betsy/faq.htm

Yes, it is customary to honor fallen soldiers every Memorial Day by placing a small flag at the gravesite. At Arlington Cemetery, on the Thursday before the Memorial Day weekend, small flags are placed at every burial site in a ceremony called "Flags In." The small flags are removed at the end of the Memorial Day weekend.

It looks like Thursday until sundown Monday on Memorial Day Weekend is acceptable.

What I have found online so far is that it is up to local custom as to the display of small flags at cemeteries. Flags at Arlington and the Marine Monument, White House and several others by law are allowed to be displayed at night at least the large flags. Nothing very clear on the small flags

I am very grateful to the volunteers in our community who take time to place and remove the flags so I am not concerned about the exact placement time and removal. I am sure it takes a generous group to devote the time to doing this and I, for one, appreciate their kindness.

In many communities members of the American Legion place the flags. In Bozeman, my cousin who is a veteran of the Korean war, and is 86 years old, has been doing this for over thirty years Often different youth groups like the Boy Scouts and Girl Scouts assist with it. Many thanks to those who serve.