Please follow the steps below.

1. Open browser and Log in web management page of the router, default IP is 192.168.1.1.   

Note: The address 192.168.1.1 is NOT on the Internet. The web-based configuration page is built into the router. 

2. Click Advanced button and enter in the main page of router.

3. Go to System Tools->Time Settings on the left side of the main page, NTP server will detect the IP address automatically if the router can access to internet. Click Save button, then Current Time will stay the same with the Internet time.

Also you can set time manually, but if router restart, reset or power off, time settings will come to defaults.