Hello guys! I decided to make this post, because I feel it will appeal to a lot of map-makers. Here is the example that I posted: http://www.planetminecraft.com/project/adjustable-countdown-timer-13w06a15/
Now you may be wondering: how will this help me? It works like this: the link leads to a world that has a countdown timer. The countdown timer uses a command block that adds the equivalent of 60 seconds to the scoreboard, because it uses a redstone clock that will take 1 out of the scoreboard every second.
This will allow you to time sequenced events with only a few pieces of redstone, instead of using about half a million repeaters. If you don't understand yet (which is completely understandable) then watch this: http://www.youtube.com/watch?v=kWOqIzevIU8 I would've embedded this, but it doesn't seem to be working.