Jesus said "no man knows the day or the hour" the Kingdom would begin in heaven.
If "the 1914 thing" could have been calculated by some verses in Second Kings and Ezekiel and Daniel, then Jesus could have calculated it back in the first century and he wouldn't have said "no one knows the day and the hour." He would have known the kingdom would begin in "1914" while he was walking the earth. Second Kings and Ezekiel and Daniel were already written then, and Jesus had a perfect mind. Jesus did not begin ruling in the Kingdom "in 1914". The start date can't be calculated using the Bible. Jesus told the disciples to stop trying to figure out "the times and seasons that belong in the Father's jurisdiction."
He did tell John about a time frame involving 3 1/2 years.
Revelation shows that after Jesus takes the throne the Devil will be kicked out of heaven, and the time of tribulation on earth will be 3 1/2 years. During that 3 1/2 years, aka "the times of the nations" or when the UN is the dominant world power, Jesus will be ruling in heaven. At the end of the 3 1/2 years, the Devil will be abyssed, and that is when the 1,000 year reign begins. Jesus will be visible at that time. Everybody will see him. Obviously that hasn't happened yet. But as far as the original thread question: "How long would Jesus' reign be?" ...the Bible says 1000 years plus 3 1/2 years. That's how long Jesus' reign will be until he turns the kingdom back over to his Father.
(But since they work together, even after that point "there will be no end to his kingdom".)