Apple doesn’t want us to change all settings in our os and the time machine backup interval is one of them. By default this backups your computer every single hour. Maybe you want to change it.
The settings are stored in a configuration file, so you can actually change the backup interval yourself editing the configuration file. But there are easier ways to do this. The free app called TimeMachineEditor will help you with it. The only thing this application does is to update the configuration file. You can schedule it to your liking. For example backup every week, or daily at night.
This little app have never had any issues, but please double-check your backup if you use third party tools like this. Obviously Apple doesn’t support using this, and Apple may change the way Time Machine works in the future.