This message indicates that the Time Of Day (TOD) clock reads zero, so its time is the beginning of the UNIX epoch: midnight, 31 December 1969. On a brand-new system, the manufacturer might have neglected to initialize the system clock. On older systems it is more likely that the rechargeable battery has run out and requires replacement.
First replace the battery according to the manufacturer's instructions. Then become superuser and use the date(1) command to set the time and date. On some systems the clock is powered by the same battery as the NVRAM, so a dead battery also causes loss of the machine's Ethernet address and host ID, which are more serious problems for networked systems.