It is difficult to determine whether or not animals, especially dogs, have a sense of the time passing. What is certain is that they have the concept of loneliness. Each breed and each individual reacts differently to your absence, but in any case, committing to become a dog owner, is above all a commitment to be there for them physically.
A social animal
As humans, dogs suffer greatly from lack of social relationships and loneliness. Permanent isolation can lead to the dog being sick, depressed and overly protective. Note that it is during these periods of solitude that dogs develop behavior problems and start barking incessantly or destroy what surrounds them. When you think that your dog has done something wrong "to annoy you," remember that your pet's life revolves around you!
Teach them to be alone
If you adopted a puppy, start teaching them to overcome loneliness as soon as they arrive. To do this, put them in a place that is familiar and comfortable and close the door without saying anything and without a profusion of caresses. Meanwhile, continue one of your daily activities as if nothing had happened. Your dog may bark, but you should not respond. After a while, when your dog is calm and silent, release them while remaining calm. You should avoid talking to them and petting them so that their "release" is not an event. Thus, they will understand that each separation is followed by reunion and that there is no reason to worry!
But when you are at home, you must not to spend all your time with them because if you're always "glued" to each other, separation will be even more difficult for them!
There are some exercises to do - if your dog is used to making a scene when they see that you are about to leave the house, a simple technique is to simulate false departures during your free time on weekends for example. Prepare yourself as if you were leaving for work by putting your coat and your shoes on and sit quietly on the couch to read or watch TV while ignoring your dog . Stay for a quarter of an hour, then get dressed normally again.
Of courses these exercises must be repeated often before your dog overcomes loneliness!