How to make sure that the clock on keenetic routers does not go astray?

Question

network hardware

there is a keenetic omny ii router
on it, the exact time is set, but every time the router is rebooted, the clock goes back about 30 minutes, and sometimes more.
it is planned to use schedules.
question: how to make the clock on the router work correctly, preferably without using external servers?

Answer 1

Make your own ntp server, if windows, then here , if linux, then here

Answer 2

Without using external servers - find the opportunity to upload your software to the router and connect a GPS receiver to it.
Or just set up NTP