Logging hours on Samsung Galaxy tab?

My mom and I are concerned about the time my sister spends on her tablet (I believe it is a tab 3). She can tell her to get off during the day but she usually disappears to her room and gets back on, and we have no idea how long she stays up doing it at night. My mom would prefer to refrain from punishment or from taking it away but wants to make sure she isn't spending too much time on it, so is there any way to log the time spent on the tablet or perhaps a possible child mode? Also she spends the vast majority of time on minecraft, so if anybody knows of a way to log hours spent on the app that would be helpful as well, thank you for any and all help!