Although Pokemon Ruby and Sapphire made little use of it, there was in fact an internal clock in those games used for events such as Shoal Cave's tide and certain evolutions.
This clock was removed in its entirety from FireRed and LeafGreen, perhaps in keeping with the spirit of the original games. As such certain concessions had to be made to reconcile some features introduced since Red and Blue.
Berries, for instance, are used for the game's Berry Crushing minigame along with their in-battle functions. Despite this, there is nowhere for the player to manually grow them - instead, there is a chance they will regenerate every 512 steps in the same spot they were found. Berries are generally found in dark patches of ground on the field and in Berry Forest.
Likewise, items may wash up on Treasure Beach under the very same conditions. The VS Seeker also works this way, though that only takes 100 steps to recharge. Finally, Daisy will offer a Pokemon a haircut again after 512 steps.
Unfortunately, the Pokemon Eevee (who evolves at different times in the day) cannot evolve into Espeon or Umbreon in these games. This means players must trade Eevee over to the Hoenn titles to evolve it or simply trade one of these Pokemon over from the Orre games to complete the Pokedex.