5th Seal Persecution When?

Revelation 6 describes a future time when the Four Horsemen will ride bringing mayhem to the world. What if they're riding today? Since the Seven Seals open silently, how would anyone know if the seals are opening?
The Fifth Seal would open after the Four Horsemen ride. What if the Fifth Seal opens soon? That would bring persecution and death to many believers. It would resemble the Last Great Persecution of Christians starting in 303 CE under Diocletian. It was horrific! Will this type of persecution start soon?
Where are we on the biblical timeline prophetically speaking?