The RTC remembers its time set, and how does the linux kernel gets this time from dev/rtc and set it as the linux time. In other words on boot up - when does kernel reads the rtc and updates its linux time.
Linux kernel has following option
RTC_HCTOSYS to restore system time from RTC on startup.
If you say yes here, the system time (wall clock) will be set using the value read from a specified RTC device. This is useful to avoid unnecessary fsck runs at boot time, and to network better.
Another way is to use a startup script, that will use
hwclock utility to set system time from RTC.