The Olivet Discourse. When Jesus said, "I come quickly", the word "quickly" translated from the Greek is "tachos". It's where we get our word "tachometer" from. It means to "speed up" or "rev up". In other words, Jesus was saying He will return when things seem to be "revving or speeding" up. His first coming fulfilled a slew of prophecies in an extremely short amount of time so the 2nd coming will be the same. When things are speeding up. Also, God said He would have to shorten the days lest there be no flesh to save... This is a side tidbit but did you know when there's a massive earthquake, it actually speeds up the rotation of the earth by a few milliseconds? Which literally shortens the day... Just something to think about.