最近處理了一些關(guān)于日期的問題，先記下來，可以后來查用。

1，將字符串轉(zhuǎn)化為日期

let formatter = DateFormatter.init()

formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

let lastTime = formatter.date(from:lastTimeString!)

2，將日期轉(zhuǎn)化為字符串

let date = Date()

let? timeFormatter = DateFormatter()

timeFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

let currentTime = timeFormatter.string(from: date as Date) as String?

3，得到兩個(gè)日期的差值

a,通過和格林威治時(shí)間比較，得到向差的秒數(shù)

let lastTime = formatter.date(from:lastTimeString!)

let currentTime = formatter.date(from:self.getCurrentTimeStamp())

let timeInterval = (currentTime?.timeIntervalSince1970)! - (lastTime?.timeIntervalSince1970)!

b,通過比較，得到相差的年月日時(shí)分秒

let ctime = date

let mtime = date2

let ctimedf = DateFormatter()

ctimedf.dateFormat = "yyyy-MM-dd HH:mm:ss"

let ctimeDate = ctimedf.date(from: ctime)

let mtimeDate = ctimedf.date(from: mtime)

let calendar = Calendar.current

let unitFlags:NSCalendar.Unit = [NSCalendar.Unit.year, NSCalendar.Unit.month , NSCalendar.Unit.day , NSCalendar.Unit.hour , NSCalendar.Unit.minute , NSCalendar.Unit.second]

let components = (calendar as NSCalendar).components(unitFlags, from: ctimeDate!, to: mtimeDate!, options: NSCalendar.Options.init(rawValue: 0))

components.hour!

components.day

components.second

components.minute!

4,獲取當(dāng)前時(shí)間的時(shí)分秒

let calendar: Calendar = Calendar(identifier: .gregorian)

var comps: DateComponents = DateComponents()

?comps = calendar.dateComponents([.year,.month,.day, .weekday, .hour, .minute,.second], from: Date())

let hour = comps.hour!? ? ? ? ? ? // 小時(shí)

?let minutes = comps.minute!? ? ? ? ? // 分鐘