Fast · Patrick Collison

Dee Hock was given 90 days to launch the BankAmericard card (which became the Visa card), starting from scratch. He did. In that period, he signed up more than 100,000 customers. 

Walt Disney's conception of "The Happiest Place on Earth" was brought to life in 366 days. 

Amazon started to implement the first version of Amazon Prime in late 2004 and announced it on February 2 2005, six weeks later.

Tony Fadell was hired to create the iPod in late January 2001. Steve Jobs greenlit the project in March 2001. They hired a contract manufacturer in April 2001, announced the product in October 2001, and shipped the first production iPod to customers in November 2001, around 290 days after getting started.

The Eiffel Tower was built in 2 years and 2 months; that is, in 793 days.