Yes, on September 30, there will be what astronomers call a "black moon."
And, yes, that does sound like it deserves to be in a movie starring Arnold Schwarzenegger fighting the devil in single combat, preferably with a longsword, in a church, as organ music plays, OK, I just realized I'm reciting the exact plot of "End of Days," a movie that involves, among other things, Arnold drinking a glass of raw egg yolks because fighting demons, uh, uses up a lot of protein.
Anyway, go watch that movie. It's wild.
OK, so a black moon, if you didn't know (I am sure you don't), occurs when a second new moon happens within the same month.
The last time this happened was over two years ago.
Now, each month there is usually a full moon and a new moon (new moon is the opposite of a full moon). And this month there will be two new moons.
A blue moon, from the expression "once in a blue moon," is what we call it when there are two full moons in one month. It is, naturally, very rare.
What this means is, when you look up at the sky, you will see only the dark side of the moon, meaning you will see nothing.
The cool thing is, however, that with no moon in the sky, you will be able to see the stars extremely clearly, as the light interference of the moon will be negated.
The black moon will appear, or disappear really, in the sky at approximately 8:11 pm ET on Friday. If you don't catch it this time around, you'll have to wait until its next appearance — in July of 2019 — when we'll all be reading or writing articles about the iPhone 9 (this one will have no screen).