Dreaming of a calendar can mean several things:
(1) You are trying to remember an important date.
(2) You have scheduled events to take note of.
(3) Time has passed and you are wondering about an issue related to the passage of time.
If you see your calendar being marked full of commitments, it can mean you are over-stretching yourself. Your dream may be a hint to slow down in waking life.
If you see your calendar being empty, it can mean this dream is a hint to socialize and make some commitments to attend events.