Which Pokémon game was the first to feature a day-and-night cycle?

Pokémon Gold and Silver were the first Pokémon games to feature a day-and-night cycle. The system used the real-world time on the Game Boy Color to divide gameplay into morning, day, and night periods.

Time affected encounters, events, and some gameplay details. Certain Pokémon appeared more readily at particular times, and some characters or activities were available only during specified parts of the day. This made the Johto region feel more dynamic than the fixed-time world of the first-generation games.

The feature was introduced alongside several other Generation II mechanics, including breeding, held items, and the Dark and Steel types. Pokémon Crystal retained the system and added further presentation changes. Later games expanded the idea with seasons, weather, and other environmental effects, but Gold and Silver established real-time progression as a recurring Pokémon design feature.