Consulting a calendar has nothing to do with you using private property owned by others. If your name is not on the deed-- you don't own it-- and you stay off of it unless you have permission. That's a basic as it gets with respect for other people's property.
What does it hurt? First, you are a liability while on their land. If you, or someone with you, gets hit by a falling tree branch or struck by lightning, the land owner is likely to get sued.
Next, your "dog walks" may be noticed by others. Even if you don't invite others to join, once they see you doing it, it encourages them to engage the same behavior. Now suppose a parent with a child is walking their dog, the child looks up just in time to be hit in the eye by a falling branch. The owner gets sued.
So what's the harm in walking across their land even if no accident happens? Simple-- establish a pattern of using that property over five years (in many jurisdictions) and you have just acquired a legal right to the walking trail you have been using. Called a prescriptive easement. Once that is established you have just harmed the owner by devaluing their land since they cannot any longer order you to leave.
A prescriptive easement exists on my land (acquired many decades ago.) It is a constant headache. In the interior of my private property, I have vehicles, dirtbikes with no mufflers, ATV's spinning tires, dogs, dust, you name it. It's my land but I can't legally force them off of the area where the easement exists. It started long ago with people believing there was no harm in taking a shortcut through the property I now own.