How can I calculate the difference between two dates?

Question

How can I calculate the days between 1 Jan 2010 and (for example) 3 Feb 2010?

Answer 1

NSTimeInterval diff = [date2 timeIntervalSinceDate:date1]; // in seconds

where date1 and date2 are NSDate's.

Also, note the definition of NSTimeInterval:

typedef double NSTimeInterval;