It says seven seals, but there are only six events. The seventh seal is just an introduction to the next angle of the story. In Rev. 6, first are the riders, and next are the saints beneath the throne. Then the great earthquake happens just before Jesus appears. The seventh is a description of the last seven years, and we do not read it until we come to Revelations 8. When do these riders appear? The two theories that, I think, fit best are strangely quite different. The first is that the white rider is a copy of Jesus and the Antichrist. That places the first rider at the start of the tribulation. The other riders then appear as the tribulation happens. Both ideas have the fourth rider appearing during the tribulation. I am going with the riders appearing over a much longer period, and their purpose is to set up the whole scenario for the end of the age. This is based on Matthew's gospel, 24:4–8, which is a description of the four horsemen. We do find the riders in Zechariah 1. I saw it at night, and behold, a man riding on a red horse! He was standing among the myrtle trees in the glen, and behind him were red, sorrel (or pale), and white horses. Four horses, but two red and none black. The black horse represents the money/political systems that have cursed the world but did not exist back then. They are sent out to patrol the earth. They change from keeping the peace to stirring up trouble. That is why I go for a longer period. Even though these riders have been around for a while, as we get closer to the end, the work of the horsemen will get more intense. It may appear that the riders are only appearing at the end, but they have been around for a while.