If you want to copy the hwclock time into system time (= displayed by date), the most straightforward command to do that would be
hwclock --hctosys --utc --noadjfile
Note that this will change system time backwards, which can be bad for databases and other applications that care about the correct ordering of timestamps.
If you must make this change while applications are running, a safer way would be to use ntpdate -B <NTP server address> to gently "slide" the system clock to the correct time.
But any of the above will not change the System clock synchronized indication at all.
The System clock synchronized comes from the kernel's timekeeping status bits: when a NTP service is running and has successfully synchronized the system clock to a NTP time source, it will flip the appropriate bits in the kernel's time_status word using the adjtimex(2) system call. The System clock synchronized is a direct interpretation of the appropriate time_status bits by systemd-timedated.
In a regular Linux system, you technically could install the optional adjtimex utility and then use adjtimex -S 0 to set the kernel's time_status word manually to the state it would normally have when NTP synchronization is in effect; but I cannot recommend this because it would be effectively just lying to yourself and your system.
Also, it appears the Photon OS may not have the adjtimex command/package available for it anyway, so the practical answer might as well be "you cannot do it without configuring NTP."
