If we're talking about emulated games, the date/time of the emulator may not have an influence on the RNG the game implements - most of the emulated systems didn't have a real time clock or the concept of the system date/time.
@Addison it all depends on how the game implemented the RNG, some of the games relied on the RAM contents to initialize the RNG. On an emulator, the emulated RAM may get initialized to the same value (zero for instance) and thus there's no RNG at stake. Some emulators cater for this kind of situation with options - for instance Snes9x has a Randomize Memory option for this kind of situations, others may initialize the RAM directly with random values to prevent RNG failures.
Funny enough, some games' RNG can be manipulated, a technique used in speedruns to get a predictable set of events/weapons/etc. An example is below, where the runner saves and resets the game during startup