Shows how to sort array of dates ascending and descending. As a extra, is supplied an NSDate extension to init NSDate from string with format yyyy/MM/dd HH:mm.

SortingDates.swift

extension NSDate {
    convenience init(fromString: String) {
        let formatter = NSDateFormatter()
        formatter.dateFormat = "yyyy/MM/dd HH:mm"
        formatter.timeZone = NSTimeZone(name: "GMT")
        let date = formatter.dateFromString(fromString) ?? NSDate()
        
        self.init(timeInterval:0, sinceDate:date)
    }
}

let date1 = NSDate(fromString: "2015/10/25 18:00")
let date2 = NSDate(fromString: "2015/10/26 18:31")
let date3 = NSDate(fromString: "2015/10/26 17:15")
let date4 = NSDate(fromString: "2015/10/26 14:45")

let arrayDates = [date1, date2, date3, date4]

arrayDates.forEach { print($0)}
//output:
//2015-10-25 18:00:00 +0000
//2015-10-26 18:31:00 +0000
//2015-10-26 17:15:00 +0000
//2015-10-26 14:45:00 +0000

arrayDates.sort { $0.compare($1) == NSComparisonResult.OrderedDescending }.forEach { print($0) }
//output:
//2015-10-26 18:31:00 +0000
//2015-10-26 17:15:00 +0000
//2015-10-26 14:45:00 +0000
//2015-10-25 18:00:00 +0000

arrayDates.sort { $0.compare($1) == NSComparisonResult.OrderedAscending }.forEach { print($0) }
//output:
//2015-10-25 18:00:00 +0000
//2015-10-26 14:45:00 +0000
//2015-10-26 17:15:00 +0000
//2015-10-26 18:31:00 +0000