The final day of September will bring a rare lunar event that hasn't occurred since March 2014. There will be a "black moon" in the sky, also known as the second new moon in a calendar month.
You may have heard of a "blue moon," which is the second full moon in a calendar month.
This type of event happens once every two and a half years.
An explanation on NASA's website says "there's really nothing to see" because it's the phase when the moon isn't visible at all, due to the moon's cycle of phases.