Sri Chinmoy: There is no hard and fast rule. There can be no categorical answer. You have to know what kind of dream you are having. Sometimes these are all imaginary dreams which come from the subconscient plane. For example, if you want to eat something, say chicken, and you don't get it, then at night the desire may be transmitted into a dream and in the dream you will be eating chicken. That kind of dream is no real dream. It is only an unfulfilled desire which comes from the subconscient plane and manifests itself in the dream state.
There are real dreams and these dreams generally take place in the small hours of the morning. We call it the Hour of God, which is between four and five o'clock in the morning. The actual hour starts at four o'clock. If you have dreams at that time they are likely to materialise. But these dreams also have to be properly guarded; they have to be without any impure thoughts. Then also, if you have dreams during a lunar eclipse or solar eclipse, these dreams are usually fulfilled.