let date:NSDate = NSDate.dateWithYear(2016, month: 2, day: 1)
print("date = \(date.yearMonthDayString)") //February 01, 2016

let date2:NSDate = NSDate.dateWithYear(2016, month: 2, day: 3, hour: 18, minute: 30, second: 25)
let date2Str:String = date2.stringWithDateFormatString("yyyy/MM/dd HH:mm:ss")
print("date2 = \(date2Str)") //2016/02/03 18:30:25

let date:NSDate = NSDate.dateWithYear(2016, month: 2, day: 18)
print("first week day in Feb. 2016 = \(date.firstWeekdayInMonth)")
//first week day in Feb. 2016 = 2

//Sunday = 1, Monday = 2, ....

let date:NSDate = NSDate.dateWithYear(2016, month: 2, day: 18)
print("number of days in Feb. 2016 = \(date.numberOfDaysInMonth)") //29

let date:NSDate = NSDate.dateWithYear(2016, month: 2, day: 18)
print("number of week in Feb. 2016 = \(date.numberOfWeekInMonth)") //5

let date:NSDate = NSDate.dateWithYear(2016, month: 2, day: 3, hour: 15, minute: 30, second: 25)
print("year: \(date.year)")
print("month: \(date.month)")
print("day: \(date.day)")
print("weekday: \(date.weekday)")
print("hour \(date.hour)")
print("minute \(date.minute)")
print("second \(date.second)")
print("nanosecond \(date.nanoSecond)")

let date:NSDate = NSDate.dateWithYear(2016, month: 2, day: 1)
let nextDate:NSDate = date.nextDate
let previousDate:NSDate = date.previousDate

print("next date: \(nextDate.yearMonthDayString)") //February 02, 2016
print("previous date: \(previousDate.yearMonthDayString)") //January 31, 2016

let startDate:NSDate = NSDate.dateWithYear(2016, month: 2, day: 1)
let endDate:NSDate = NSDate.dateWithYear(2016, month: 2, day: 4)
let days:Int = startDate.daysToDate(endDate)

print("\(endDate.stringWithDateFormatString("yyyy/MM/dd")) - \(startDate.stringWithDateFormatString("yyyy/MM/dd")) = \(days)")
//2016/02/04 - 2016/02/01 = 3

let date:NSDate = NSDate.dateWithYear(2016, month: 2, day: 3, hour: 15, minute: 32, second: 24)
print("\(date.yearMonthString)") //February 2016
print("\(date.yearMonthDayString)") //February 03, 2016
print("\(date.yearMonthDayWeekdayString)") //Wed, February 03, 2016
print("\(date.yearMonthDayStringShortStyle)") // 2/3/16
print("\(date.yearMonthDayStringMediumStyle)") //Feb 3, 2016

print("\(date.stringWithDateFormatterStyle(NSDateFormatterStyle.FullStyle))") //Wednesday, February 3, 2016
print("\(date.stringWithDateFormatString("yyyy/MM/dd HH:mm:ss"))") //2016/02/03 15:32:24

let date1:NSDate = NSDate.dateWithYear(2016, month: 2, day: 1)
let comp1:NSDateComponents = NSDateComponents()
comp1.day = 5
let date2:NSDate = date1.dateByAddingComponents(comp1)

print("date2 \(date2.yearMonthDayString)") //February 06, 2016