How to do the time setting ? Whenever am setting the time, it’s changed default by automatically, like when ever i used to change the time to present time, but it will change to default Date & time Jan/02/1970, 05:45:33

That’s normal for routerboards as they don’t have the batteryy installed. I suggest (if this router has access to internet) to use NTP client service, which will sync routers time chronologically with a NTP server.
where will be there is service!!!
I don’t understand, sorry.
Change to your needs
ntp is under system ntp client
/system clock
set time-zone-name=America/New_York
/system ntp client
set enabled=yes mode=unicast primary-ntp=129.6.15.28 secondary-ntp=129.6.15.29