Gold and Silver were the first games to use an internal clock, and this was kept synchronised (i.e. so it would be at the correct time when you next played) by the internal battery in the game cartridge. In the time since Gold and Silver's release the internal batteries were drained completely; they lasted around seven years, if I remember correctly. The internal battery was also used to save the game to memory, and thus, because it was completely spent, the vast majority of Gold and Silver games are unsavable. This only happens if you have a save file on the cartridge, though; my Silver version hasn't had a save file on it for years, so it still works, as far as I know. 8D