Dogs do understand time, but not in the same way that humans do. They can learn to associate certain events with certain times of day, such as mealtime or going for a walk.
Dogs perceive time in a linear fashion, meaning that they can understand that one event happens before or after another event.
The difference between day and night
Dogs learn about time through a combination of conditioning and experience.
Give your dog plenty of opportunities to learn about the passage of time, such as by taking them for walks at different times of day.
It helps them to anticipate events, such as mealtime or going for a walk. It also helps them to learn and follow rules.