Time
Ah, time. One of the universe's biggest mysteries. Is it linear, or is it cyclical? Are those the only two options?
Well, for now we'll assume that time is linear. That's how it seems to us, anyway.
Project Alpha contains a nifty time system.
Day/Night
There are four different parts of the day. Morning, Day, Evening, and Night.
These matter because, just like in real life, you'll only see some creatures at certain times of the day. I mean, when have you ever seen a bugbear sitting in the forest at 7 A.M. drinking lemonade? Each day in-game is 24 minutes in real life. Fear not, for you will be able to sleep and rest to make time pass quicker.
Seasons
Yes, there will even be seasons! Spring, summer, fall, and winter.
Each season is 10 in-game days long.
Keep your eyes open, though, because those hellish imps have been known to make and behead snowmen!
Moon Phases
There will be different moon phases. That way, if there's certain creatures that are known for only existing during certain moon phases *cough*werewolf*cough*, you'll encounter them during those moon phases.