Pokémon Crystal was revolutionary for its real-time clock system, which influences many aspects of the game. Understanding how the time system works is key to accessing certain Pokémon, items, and events.
- Day/Night Cycle: The game world changes between day (4:00 AM - 5:59 PM), night (6:00 PM - 3:59 AM), and morning/evening transitions. Different wild Pokémon appear at different times (e.g., Hoothoot at night, Ledyba during the day).
- Daily Events: Many NPCs offer daily services or items. For example, the Haircut Brothers in Goldenrod City can increase your Pokémon's happiness once a day. The woman in the Goldenrod Dept. Store basement gives out a different item daily.
- Weekly Events: The Bug-Catching Contest in National Park occurs on Tuesdays, Thursdays, and Saturdays. The Move Tutor in Blackthorn City can teach a powerful move once a week.
- Day of the Week Specific Pokémon: Certain Pokémon only appear on specific days. For instance, Lapras appears in Union Cave only on Fridays.
- Happiness (Friendship): The time of day can influence happiness gains. Walking around, winning battles, and using certain items (like vitamins) increase happiness, which is required for some evolutions (e.g., Espeon, Umbreon, Togetic).
Adjusting your Game Boy Color's internal clock can be used to manipulate these events, but be aware that excessive time manipulation can sometimes have minor in-game consequences or be seen as cheating by some players.