Describe a scenario where you want to reduce your Amazon Elastic Compute Cloud $($Amazon EC$2)$ service usage. You decide you want to stop instances at a predefined time. For example, you want to stop EC$2$ instances at night $($when less capacity is needed$),$ and then start the instances back up in the morning $($before the workday starts$)$; explain with an example that how would you achieve this by outlining what happens at each step? Also, mention different $$event sources$$ that can be used to initiate the automation function.