An example of dealing with NSDate in Swift

NSDateMath.swift

import Foundation

// MARK: Comparable instance for NSDate
public func <(a: NSDate, b: NSDate) -> Bool {
    return a.compare(b) == .OrderedAscending
}

public func ==(a: NSDate, b: NSDate) -> Bool {
    return a.compare(b) == .OrderedSame
}

extension NSDate : Comparable {}

// MARK: Examples:

let now      = NSDate()
let tomorrow = now.dateByAddingTimeInterval(24 * 3600)
let yesteday = now.dateByAddingTimeInterval(-24 * 3600)
let minuteAgo = now.dateByAddingTimeInterval(-60)
let dates: [NSDate] = [now, tomorrow, yesteday, minuteAgo]

sorted(dates)
minElement(dates) // Watch out here: minElement crashes for empty arrays!
maxElement(dates) // ...maxElement likewise!