test NSdate according to http://www.appcoda.com/nsdate/

NSdateTest.swift

import AppKit

let currentDate = NSDate()
//NSDate
//NSDateFormatter
//NSDateComponents
//NSDateComponentFormatter
//NSCalendar

//let dateComponents = NSDateComponents()
//let day = dateComponents.day
//let month = dateComponents.month


let dateFormatter = NSDateFormatter()

dateFormatter.locale = NSLocale(localeIdentifier:  "en_GB")

let chinaLocale =  NSLocale(localeIdentifier: "zh_CN")

dateFormatter.dateStyle = NSDateFormatterStyle.FullStyle

var convertedDate = dateFormatter.stringFromDate(currentDate)



dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
convertedDate = dateFormatter.stringFromDate(currentDate)

var dateAsString = "2016-07-24 16:45:49"
var newDate = dateFormatter.dateFromString(dateAsString)


let calendar = NSCalendar.currentCalendar();

let dateComponents = calendar.components([NSCalendarUnit.Day, NSCalendarUnit.Month, NSCalendarUnit.Year, NSCalendarUnit.WeekOfYear, NSCalendarUnit.Hour, NSCalendarUnit.Minute, NSCalendarUnit.Second, NSCalendarUnit.Nanosecond], fromDate: currentDate)



print("day = \(dateComponents.day)", "month = \(dateComponents.month)", "year = \(dateComponents.year)", "week of year = \(dateComponents.weekOfYear)", "hour = \(dateComponents.hour)", "minute = \(dateComponents.minute)", "second = \(dateComponents.second)", "nanosecond = \(dateComponents.nanosecond)" , separator: ", ", terminator: "")



let components = NSDateComponents()
components.day = 5
components.month = 01
components.year = 2016
components.hour = 19
components.minute = 30
newDate = calendar.dateFromComponents(components)

components.timeZone = NSTimeZone(abbreviation: "GMT")
newDate = calendar.dateFromComponents(components)

dateFormatter.dateFormat = "MMM dd, yyyy zzz"
dateAsString = "Oct 08, 2015 GMT"
var date1 = dateFormatter.dateFromString(dateAsString)!

dateAsString = "Oct 10, 2015 GMT"
var date2 = dateFormatter.dateFromString(dateAsString)!

print("Earlier date is: \(date1.earlierDate(date2))")
print("Later date is: \(date1.laterDate(date2))")


if date1.compare(date2) == NSComparisonResult.OrderedAscending {
    print("Date1 is Earlier than Date2")
}

if date1.timeIntervalSinceReferenceDate <  date2.timeIntervalSinceReferenceDate {
    print("Date1 is Earlier than Date2")
}
let monthsToAdd = 1

let daysToAdd = 1

var calculatedDate = NSCalendar.currentCalendar().dateByAddingUnit(NSCalendarUnit.Month, value: monthsToAdd, toDate: currentDate, options: NSCalendarOptions.init(rawValue: 0))
calculatedDate = NSCalendar.currentCalendar().dateByAddingUnit(NSCalendarUnit.Day, value: daysToAdd, toDate: calculatedDate!, options: NSCalendarOptions.init(rawValue: 0))




let newDateComponents = NSDateComponents()
newDateComponents.month = monthsToAdd
newDateComponents.day = daysToAdd

calculatedDate = NSCalendar.currentCalendar().dateByAddingComponents(newDateComponents, toDate: currentDate, options: NSCalendarOptions.init(rawValue: 0))


let hoursToAddInSeconds: NSTimeInterval = 90 * 60
calculatedDate = currentDate.dateByAddingTimeInterval(hoursToAddInSeconds)

let hoursToSubInSeconds: NSTimeInterval = -90 * 60
calculatedDate = currentDate.dateByAddingTimeInterval(hoursToSubInSeconds)


dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
dateAsString = "2015-10-08 14:25:37"
date1 = dateFormatter.dateFromString(dateAsString)!

dateAsString = "2018-03-05 08:14:19"
date2 = dateFormatter.dateFromString(dateAsString)!

var diffDateComponents = NSCalendar.currentCalendar().components([NSCalendarUnit.Year, NSCalendarUnit.Month, NSCalendarUnit.Day, NSCalendarUnit.Hour, NSCalendarUnit.Minute, NSCalendarUnit.Second], fromDate: date1, toDate: date2, options: NSCalendarOptions.init(rawValue: 0))

print("The difference between dates is: \(diffDateComponents.year) years, \(diffDateComponents.month) months, \(diffDateComponents.day) days, \(diffDateComponents.hour) hours, \(diffDateComponents.minute) minutes, \(diffDateComponents.second) seconds")

let dateComponentsFormatter = NSDateComponentsFormatter()
dateComponentsFormatter.unitsStyle = NSDateComponentsFormatterUnitsStyle.Full

let interval = date2.timeIntervalSinceDate(date1)
dateComponentsFormatter.stringFromTimeInterval(interval)