It's

not the astronomy that is unique, 

it's the condition here on earth that is.

"As EarthSky notes, however, the alignment of the constellation is not that unique in history.

"From the standpoint of astronomy, there's nothing unique or unusual about the sun, moon and planets - or the constellation Virgo - on September 23, 2017, despite claims on the Internet of a unique and significant celestial event, supposedly "mirroring" the Bible's Book of Revelation," astronomer Christopher M. Graney said. "In the past 1,000 years, this same event has happened at least four times already, in 1827, 1483, 1293, and 1056."

Those times weren't now.

It's not what has happened in the heavens that is unique, it's the condition of the earth at the time of the astronomy that is.