I think it depends upon what stage the turkeys are in, kinda like pre-rut and post rut....

I have had birds on the ground by 7:30 in the morning the first week of the season, before they get henned up...
This past Saturday, I called in a bird for my buddy and he killed it at 7:10am...This bird came running in to the decoys...

I have also called them in as late as 6:00 in the evening, when they were looking for a hen...

And...Just like during the rut, I have killed them in the middle of the day, after they left the hen they picked up in the morning and then went looking for another...I feel this is the best strategy after the first week or two, after everyone else has given up because they think the birds are either henned up or call shy...I do call less at this time and use more purrs, I also call softer...A good place to start this is where he picked up his hens in the morning, or a green field...

I try to stay in tune with the birds and time my hunts accordingly...