Poetic nightfall' is a phrase that describes the beauty of a sunset. It is often used to describe the peacefulness and serenity of the end of the day, when the sun is setting and the sky is filled with vibrant colors. The term 'poetic nightfall' can also be used to describe the feeling of calmness and tranquility that comes with the end of the day. EEN is an acronym for Evening, which is the time of day when nightfall occurs.