两个NSDate之间的小时差异

let date1 = NSDate()
let date2 = NSDate(timeIntervalSince1970: TimeInterval(365 * 24 * 60 * 60))

let component1 = NSDateComponents()
component1.year = 2000
component1.month = 1
component1.day = 1
component1.hour = 0

let component2 = NSDateComponents()
component2.year = 2000
component2.month = 12
component2.day = 31
component2.hour = 23

let difference = NSDateComponents(timeIntervalSinceDate: component2) - NSDateComponents(timeIntervalSinceDate: component1)

let hoursDifference = String(format: "%d hours", difference.hour)