Swift 3.0:将服务器UTC时间转换为本地时间,反之亦然

Question

我想将服务器UTC时间转换为本地时间,反之亦然.这是我的代码..

var isTimeFromServer = true
var time:String!
var period:String!
let timeString = "6:59 AM" //Current UTC time

if isTimeFromServer {

    let index = timeString.index(timeString.startIndex, offsetBy: 5)
    let twelve = timeString.substring(to: index)

    var dateString:String!

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "H:mm"
    let date12 = dateFormatter.date(from: twelve)!

    dateFormatter.dateFormat = "h:mm a"
    let date22 = dateFormatter.string(from: date12)

    //print(date22)
    dateString = date22
    //print("dateString=\(dateString)")

    time = dateString.components(separatedBy: " ")[0]
    period = dateString.components(separatedBy: " ")[1]

}
else {
    time = timeString.components(separatedBy: " ")[0]
    period = timeString.components(separatedBy: " ")[1]
}

var hour = Int(time.components(separatedBy: ":")[0])

hour = period == "AM" ? hour : hour! + 12
let minute = Int(time.components(separatedBy: ":")[1])
let calender = NSCalendar.current
var datecomponent = DateComponents()
datecomponent.calendar = calender
datecomponent.hour = hour
datecomponent.minute = minute

if !isTimeFromServer {
    // local to UTC
    datecomponent.timeZone = TimeZone.current
}
else {
    datecomponent.timeZone = TimeZone(abbreviation: "UTC")
}

let date = datecomponent.date
let dateFormatter = DateFormatter()

if !isTimeFromServer {
    dateFormatter.dateFormat = "H:mm"
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    dateFormatter.string(from: date!)
}
else {
    //UTC to local
    dateFormatter.dateFormat = "h:mm a"
    dateFormatter.timeZone = TimeZone.current
    dateFormatter.string(from: date!)
}

我得到当地时间

o/p:"12:52 PM"

但实际的当地时间和输出时间差是23分钟.

Answer 1

我不知道你的代码有什么问题.
但看起来太多不必要的东西,比如你正在设置日历,从字符串中获取一些元素.这是我的小版本的UTCToLocal和localToUTC函数.
但为此,您需要以特定格式传递字符串.因为我已经解开了日期对象.但您可以使用一些防护条件来防止应用程序崩溃.

func localToUTC(date:String) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "h:mm a"
    dateFormatter.calendar = NSCalendar.current
    dateFormatter.timeZone = TimeZone.current

    let dt = dateFormatter.date(from: date)
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    dateFormatter.dateFormat = "H:mm:ss"

    return dateFormatter.string(from: dt!)
}

func UTCToLocal(date:String) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "H:mm:ss"
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")

    let dt = dateFormatter.date(from: date)
    dateFormatter.timeZone = TimeZone.current
    dateFormatter.dateFormat = "h:mm a"

    return dateFormatter.string(from: dt!)
}

并调用这些函数如下.

print(UTCToLocal(date: "13:07:00"))
print(localToUTC(date: "06:40 PM"))

希望这会帮助你.
快乐的编码!!

Answer 2

Mrugesh的答案是完美的,但是如果有人需要使用他们自己的格式,或者使用某种不同的格式,我会将其推广,这样你就可以在两个参数中给出不同的格式或相同的格式.

func localToUTC(date:String, fromFormat: String, toFormat: String) -> String {

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = fromFormat
    dateFormatter.calendar = NSCalendar.current
    dateFormatter.timeZone = TimeZone.current
    dateFormatter.date
    let dt = dateFormatter.date(from: date)
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    dateFormatter.dateFormat = toFormat

    return dateFormatter.string(from: dt!)
}

func UTCToLocal(date:String, fromFormat: String, toFormat: String) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = fromFormat
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")

    let dt = dateFormatter.date(from: date)
    dateFormatter.timeZone = TimeZone.current
    dateFormatter.dateFormat = toFormat

return dateFormatter.string(from: dt!)
}

let localDateAsString = UTCToLocal(date: dateAsString!, fromFormat: "hh:mm a, dd MMM yyyy", toFormat: "hh:mm a, dd MMM yyyy")

你可以像上面一样使用它.希望能帮助到你.

Answer 3

要将 UTC 日期转换为本地系统日期，您可以使用以下日期扩展：

extension Date {

    // Convert local time to UTC (or GMT)
    func toGlobalTime() -> Date {
        let timezone = TimeZone.current
        let seconds = -TimeInterval(timezone.secondsFromGMT(for: self))
        return Date(timeInterval: seconds, since: self)
    }

    // Convert UTC (or GMT) to local time
    func toLocalTime() -> Date {
        
        // 1) Get the current TimeZone's seconds from GMT. Since I am in Chicago this will be: 60*60*5 (18000)
        let timezoneOffset = TimeZone.current.secondsFromGMT()
        
        // 2) Get the current date (GMT) in seconds since 1970. Epoch datetime.
        let epochDate = self.timeIntervalSince1970
        
        // 3) Perform a calculation with timezoneOffset + epochDate to get the total seconds for the
        //    local date since 1970.
        //    This may look a bit strange, but since timezoneOffset is given as -18000.0, adding epochDate and timezoneOffset
        //    calculates correctly.
        let timezoneEpochOffset = (epochDate + Double(timezoneOffset))
        
        
        // 4) Finally, create a date using the seconds offset since 1970 for the local date.
        return Date(timeIntervalSince1970: timezoneEpochOffset)
    }

}

Answer 4

在Mrugesh Tank Answer的帮助下,

我更新了他的答案并创建了日期的扩展名.这样您就可以从ViewController或者来自单元类的任何地方轻松访问这些函数.

extension String {

  //MARK:- Convert UTC To Local Date by passing date formats value
  func UTCToLocal(incomingFormat: String, outGoingFormat: String) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = incomingFormat
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")

    let dt = dateFormatter.date(from: self)
    dateFormatter.timeZone = TimeZone.current
    dateFormatter.dateFormat = outGoingFormat

    return dateFormatter.string(from: dt ?? Date())
  }

  //MARK:- Convert Local To UTC Date by passing date formats value
  func localToUTC(incomingFormat: String, outGoingFormat: String) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = incomingFormat
    dateFormatter.calendar = NSCalendar.current
    dateFormatter.timeZone = TimeZone.current

    let dt = dateFormatter.date(from: self)
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    dateFormatter.dateFormat = outGoingFormat

    return dateFormatter.string(from: dt ?? Date())
  }
}

示例如何使用它: -

Note:- eventStartDate is the string which you have to converted in your format like this:- "2018-07-11T16:22:00.000Z" 

let finalDate = eventStartDate.UTCToLocal(incomingFormat: "yyyy-MM-dd'T'HH:mm:ss.SSSZ", outGoingFormat: "MMM d, yyyy h:mm a")