Time schedules are a clear way to automate actions based on time. For instance, you can make an action take place at the same time every day, or you can set a week/weekend programme. With the Periodic time schedule you go a step further: you can use it to automate actions in different periods, for instance the winter period (lights are on longer, heating is on more often) and the summer period (lights are on less, the temperature of the swimming pool can be a little lower).
You can create and manage a time schedule, but actions are only performed when you use the time schedule in a Conditional action.