I assume this would be a custom implementation. For example, tag an EC2 instance with "CronStart: 0 8 * * " and "CronStop: 0 17 * *". Then have a service that

I assume this would be a custom implementation. For example, tag an EC2 instance with "CronStart: 0 8 * * " and "CronStop: 0 17 * *". Then have a service that queries EC2 instances with CronStart/CronStop tags, and start/stop the instances according to these schedules. I haven't looked for any services that does this out-of-the-box, but it would not particularly complicated to implement on e.g. AWS Lambda.