According to a report on iClarified.com, MacMagzine.com.br reader JosZe' discovered a counter embedded in the code for Apple's home page. The code checks to see if the time and date on your computer is past the time and date that the billionth iPhone app is downloaded. Currently, that time is estimated to be 14:12:20 on April 23, but you can bet that between now and then, Apple will tweak and adjust its estimate as required.
This much-anticipated event comes less than one year after the iTunes App Store opened--an astounding nine months. In contrast, the iTunes Music Store had only sold 70 million songs its first year and a billion in approximately three years.
The new page that will appear after the billionth download is shown below. The original report, translated from Portuguese, is here.