@WiggidyZooty 

Hi,

Home-grade routers usually do not have a battery-buffered timekeeper device to carry date and time trough a reset or a power-off period.

Sure, if the router is gracefully rebooted TP-Link could actually store the current time and date to flash memory before shutdown and then read it again from flash memory once the router's Linux system has booted up again. Apparently they didn't do that, maybe because ultimately there is no way of knowing how long the router was actually down and hence the time and even the date could be off quite a bit then.

In case there is a computer connected to the Archer A7 that is running 24/7, then you could setup a local NTP Server from which the Archer A7 can retrieve date and time automatically. On Windows 10 the NTP server can be enabled with a bit of effort and Windows Server and Linux should have been able to do this long since.