I'm not quite sure what your problem was, but I will tell you how to use a timer as well as the neat features it has!
To set the Family Timer
On your console, go to Settings, and then select Family.
Tip Not seeing Settings? You might be using an older version of the console software. See Update your Xbox 360 console software for information on how to update your console software.
Select On to turn on Console Safety.
Enter a 4-button pass code using your controller.
Select Family Timer.
Select whether you want to set a Daily or Weekly timer.
Move down to the time period and use the left stick to increase or decrease the time period, then select Continue.
Select Save and Exit.
When the Family Timer is on, notifications will appear 1 hour, 30 minutes, 15 minutes, and 5 minutes before the time runs out. These give players sufficient warning so that they can save their games. However, when one of these notifications appear, you can
add time or disable the timer altogether by entering the pass code.
To add time or suspend the Family Timer
When a Family Timer notification appears, press the Guide button to see the Family Timer options.
Enter your pass code using your controller.
Choose to add more time, suspend the timer, or turn the console off.
Note: these settings can either be daily or weekly allowances.