I started HeartGold yesterday, and already I'm experiencing problems.

At the moment I'm training on Route 31. It's almost 9pm right now according to my DS, and the scenery does show that it's nighttime. However, I'm coming across Pokémon that do not appear at night, including Pidgey, Caterpie and Metapod. Is it a problem with the game itself, or am I hallucinating?