2012- not enough time!

The Mile High Tower started construction on January 13, 2008. How do they think that they will be able to build a 1600 meter tower by 2012, which is only 4 years. The Burj Dubai which started construction in 2004 is now 600 meters in 2008, so the general rule is that in 4 years a building will reach about 600 meters. This would mean that the Mile High Tower shouldn't be done until at least 2022. Why do buildings give very short periods of construction time when they can never follow through. Why not give enough time for the building to actually be done. Like the Burj Dubai will not stand at 818-1011 meters by December 30, 2008. They are too far behind. Any comments or opinions?

First of all contractors give shorter time periods because they have to compete to get the contract and the guy who says he can get it done the fastest will get the job...
Ohk, there is no such thing as a general rule of a building reaching any height, my house took 3 years to build, and it's only got three floors...
The design of the building, how intricate the work is, etc etc all influence how fast the building is made, not how high it has to be...

Burj Dubai update:
Currently as of March 30, 2008 the tallest tower ever built is the Burj Dubai at 650 meters tall. The tallest Freestanding structure in the world is the Burj Dubai, still under construction. The Burj Dubai is the tallest skyscraper, tallest freestanding structure, and tallest manmade structure of any sort or kind ever to be built on the face of the planet Earth in its 4.54 billion years of history. The Burj Dubai will rise to around 950-1011 meters tall.