It took Apple 74 days to sell one million iPhones and 28 days to sell one million iPads

"To put [Apple Watch figures not yet revealed] in context: It took Apple 74 days to sell one million iPhones and 28 days to sell one million iPads. So even if sales are constrained by supply, it still likely represents a significant increase in momentum from previous new Apple products."
Source:  Mashable, 13th April 2015
Links -
74 days to sell 1m iPhones - 10th September 2007 (Press release also points out that it took nearly 2 years to sell 1m iPods)
(Note that the iPhone wasn't released in UK and other major markets until after this point)
28 days to sell 1m iPads - 3rd May 2010
Over 300,000 iPads sold in first day - 5th April 1010