The term "am horizon" refers to the time of day when the sun rises and the sky turns from dark to light. Opposite to "am horizon" is "pm horizon," which signals the end of the day as the sun starts to set and darkness falls. While "am horizon" suggests a fresh start, new opportunities, and a sense of hopefulness, "pm horizon" brings forth a feeling of finality and closure. Other antonyms of "am horizon" could be "midnight," "dusk," or "sunset," all of which symbolize the end of one day and the beginning of another.