System time is the total duration for which your Tp-link router is being operated by a user. A user can efficiently utilize the System Time to determine the time that he spends on the internet. You can also control the System time function for controlling the other time-based functions like Parental Control, Access Schedule, Block services, Keyword filter, and various other functions of the tplinkwifi.net window. You can configure it using the Time settings option of the web interface of the Tplink router.