The last time this green comet was visible from earth was around 50,000 years ago.

https://www.space.com/green-comet-close-approach-skywatcher-photos

Many years ago, my maternal grandmother told me that she saw Halley’s Comet in 1910 when she was a young child, living in Canada.

The passing of a comet is said to signify a time of great upheaval and change.