AWS EC2 Container Service official webpage says:
There is no additional charge for Amazon EC2 Container Service. You pay for AWS resources (e.g. EC2 instances or EBS volumes) you create to store and run your application.
What does that mean if I host my application that would run on the micro EC2 instance and it would have been scheduled to run only once a day. The execution would take 1 hour.
Does it mean I pay for 1 hour or do I also pay for the EC2 instance while it's idle? Is in this case AWS Beanstalk better?
what do you mean idle ?
In AWS EC2 from pricing point of view an instance is running or stopped - if your instance is terminated, there's no instance so you don't pay.
If your instance is running you pay for it, wether you have some execution code or not.
If your instance is stopped, you don't pay for EC2 usage but you will still pay for other charges : if you have an elastic IP address you will pay for it, if you have EBS storage you will pay for it.
Note: remember that cloud is about maximizing the resources you use. if you dont use the resources, stop them so you don't get charge.
You can read about the aws blog
Resource Efficiency – A containerized application can make very efficient use of resources. You can choose to run multiple, unrelated containers on the same EC2 instance in order to make good use of all available resources. You could, for example, decide to run a mix of short-term image processing jobs and long-running web services on the same instance.