Here is the interpretation of the dragon in Revelation 12.
As other people have said, the dragon is the constellation draco. It's seven heads are the seven stars in the head of draco constellation (3 are faint), the seven crowns are the seven stars in corona borealis, and the 10 horns are the 10 stars in bootes.
But what is important here is the specific date is specified by the dragon sweeping 1/3 the stars from the sky. This date is precisely December 25th 2017. (Or just december 25th in general). How do we know this? Stars falling from the sky to earth are meteor showers. You may not know this but meteor showers are centered in a single position in the sky and come at the exact same time every year. So I looked for meteor showers that were close enough to draco that it could sweep them with its tail. Turns out there are two, one above it's tail and one below its tail. Ursids is the one below his tail.
Now what does the one third of the stars in the sky mean? Well usually there are more than one meteor showers happening at once. But there is only one day a year when the ursids is exactly one of three active meteor showers, december 25th.
So this is part of the revelation 12 prophecy. That on december 25th Jesus was born and the dragon tried to place a pagan holiday on this date to overshadow the date of christ's birth, emperor Aurelian did this. He was the second beast and antichrist after the alignment in August 28th 249 AD as I mentioned in the edit of my post "The period of witness is here".
Also in the 249 AD revelation 12 alignment jupiter is still in Virgo on december 25th which is very very rare.
Cyprian and Novation were the Two Witnesses of that time and they were both killed by the first beast shortly after the first beast was revealed, Emperor Valerian, 7 years after the 249 alignment. In around 256-257 Valerian became the beast and started persecuting christians. But the persecution of christians started just after the revelation 12 sign in 249 happened.
The second beast or antichrist was Aurelian who came shortly after Valerian and turned the hearts of the people back to the sun god who valerian also caused the people to worship and everyone who refused were persecuted or put to death.
So in fact the revelation 12 sign may have in fact been fulfilled december 25th 249 AD. However I think the sign is applicable now too and we will have another beast coming 7 years from now as well in 2024.