On iOS 12 you can now limit the amount of time spent each day in particular apps or types of apps. To configure app time limits, Screen Time needs to be enabled on your iOS device (instructions on enabling Screen Time).
- Launch the iOS Settings app from the Home screen.
- Tap Screen Time.
- Tap App Limits.
- Tap Add Limit.
- Choose the apps and types of apps you want managed by this time limit and then tap Add.
- Choose the maximum amount of time per day you want these apps to be used (you can also customize the limit for each day of the week). Then tap App Limits to save the limit.
You're done! You can tap Add Limit to add more time limits or exit out of Screen Time.