What is your routine like?
I would suggest a good walk/exercise in the morning first thing - depending on the age of your dog of course but a good run/walk for an hour at the start of the day is the best way IMO to get a calm dog for the rest of the day...

When I need my boy to be calm during the day (for instance if I have an important paper to write and although ill be home I need peace and quiet) I ask my OH to tire him out in the morning, then I feed him...he'll be resting and calm until the middle of the afternoon
Then in the afternoon Ill do a training session with him to stimulate him mentally - before he goes for his evening walk, with either me or OH.

And I agree with the post above as well

xx