Time preferences
Use the Time pane of Parental Controls System Preferences to limit the number of hours a day a child can spend on the Mac, and restrict the Mac during school nights and weekend hours.
To view these preferences, choose Apple menu > System Preferences, click Parental Controls, click the lock icon 
to unlock it, then enter an administrator name and password (or if your Mac has a Touch Bar, use Touch ID). Select a user, then click Time.
Open Parental Controls preferences for me
Weekday time limits | To set a maximum amount of time that the child can use the Mac during the week (Monday through Friday), select “Limit weekday use to” then drag the slider to adjust the number of hours per day the child can use the Mac. |
Weekend time limits | To set a maximum amount of time that the child can use the Mac during the weekend, select “Limit weekend use to” then drag the slider to adjust the number of hours per day the child can use the Mac. |
Bedtime | You can prevent a child from using the Mac during time reserved for sleep or other activities. To restrict the Mac on Sunday through Thursday nights, select “School nights,” then specify the time period when the Mac can’t be used. To restrict the Mac on Friday and Saturday nights, select Weekend, then specify the time period when the Mac can’t be used. |
Logs | Monitor a child’s use of the Mac. Click Logs to get information on the child’s app and Internet activities. For more information, see Monitor children’s computer usage. |