NTP problem

hi,
I have setup ntp client in router and set 4.2.2.2 and 4.2.2.4 as primary and secondary ntp server, but when i reboot the router or shut it down, the time goes back in time ( ..1970) how should i prevent this and make the router to update the time even if it is rebooted ?!
( router has connection to internet all the time )

Changelog for 6.17:

*) time - on routerboards, current time is saved in configuration on reboot
and on clock adjustment, and is used to set initial time after reboot;

System / SNTP Clinet / enable=yes
primary: 4.2.2.4
secondary: 4.2.2.8


OR:
IP / cloud / enable=yes , update time: yes