Swift 3.0 : Convert server UTC time to local time and vice-versa

Question

I want to convert server UTC time to local time and vice-versa. Here is my code..

var isTimeFromServer = true
var time:String!
var period:String!
let timeStr         


        

Answer 1

I don't know what's wrong with your code.
But looks too much unnecessary things are there like you're setting calendar, fetching some elements from string. Here is my small version of UTCToLocal and localToUTC function.
But for that you need to pass string in specific format. Cause I've forcly unwrapped date objects. But you can use some guard conditions to prevent crashing your app.

func localToUTC(dateStr: String) -> String? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "h:mm a"
    dateFormatter.calendar = Calendar.current
    dateFormatter.timeZone = TimeZone.current
    
    if let date = dateFormatter.date(from: dateStr) {
        dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
        dateFormatter.dateFormat = "H:mm:ss"
    
        return dateFormatter.string(from: date)
    }
    return nil
}

func utcToLocal(dateStr: String) -> String? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "H:mm:ss"
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    
    if let date = dateFormatter.date(from: dateStr) {
        dateFormatter.timeZone = TimeZone.current
        dateFormatter.dateFormat = "h:mm a"
    
        return dateFormatter.string(from: date)
    }
    return nil
}

and call these function like below.

print(utcToLocal(dateStr: "13:07:00"))
print(localToUTC(dateStr: "06:40 PM"))

Hope this will help you.
Happy coding!!

Answer 2

By the help of Mrugesh Tank Answer,

I have updated his answer and creating the extensions for the date. So that you can easily access the functions from anywhere either from ViewController or either from cell class as well.

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())
  }
}

Example how to use it:-

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")

Answer 3

You can use in swift 4/5

  var myDate:String = "2020-02-18 14:30:57"
    var convertedLocalTime:String = ""

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd H:mm:ss"

    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")

    if let dt = dateFormatter.date(from: myDate) {
        dateFormatter.timeZone = TimeZone.current
        dateFormatter.dateFormat = "yyyy-MM-dd h:mm a"
        convertedLocalTime = dateFormatter.string(from: dt)
    } else {
        print("There was an error decoding the string")
    }

    print("convertedLocalTime--",convertedLocalTime)

Answer 4

For everyone using TimeZone objects. I would advise you to create your TimeZone from identifier rather than abbreviation when you have the possibility.

This prevents errors caused by daylight saving.

To illustrate my point let's take an example. You can instantiate like this let timeZone = TimeZone(identifier: "Europe/Paris") or like that let timeZone = TimeZone(abbreviation: "CEST") or "UTC +2:00"

But this is time zone for summer CEST meaning Central Europe Summer Time We have CET meaning Central Europe Time for winter which is "UTC +1:00"

You could manage daylight saving by your own with Date.isDaylightSavingsTime but this means more code and you don't have control on where your daylight saving sprang from. "indicates whether the receiver is currently using daylight saving time" from official doc

All is that is to say favour TimeZone(identifier: ...)

Answer 5

Please try it:

func convertUTCToLocal(timeString: String) -> String? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "h:mm a"

    dateFormatter.timeZone = TimeZone.init(abbreviation: "UTC")
    let timeUTC = dateFormatter.date(from: timeString)

    if timeUTC != nil {
        dateFormatter.timeZone = NSTimeZone.local

        let localTime = dateFormatter.string(from: timeUTC!)
        return localTime
    }

    return nil
}



func convertLocalToUTC(localTime: String) -> String? {

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "h:mm a"
    dateFormatter.timeZone = NSTimeZone.local
    let timeLocal = dateFormatter.date(from: localTime)

    if timeLocal != nil {
        dateFormatter.timeZone = TimeZone.init(abbreviation: "UTC")

        let timeUTC = dateFormatter.string(from: timeLocal!)
        return timeUTC
    }
    return nil
}


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


    if isTimeFromServer {
        print(convertUTCToLocal(timeString: timeString))
    } else {
        print(convertLocalToUTC(localTime: timeString))
    }

Answer 6

If you need to convert timestamp you can use timezoneOffset like here:

if let dateStr = model.date, let dateInt = Int(dateStr) {
            let timezoneOffset =  TimeZone.current.secondsFromGMT()
            let localDateInt = dateInt + timezoneOffset
            let date = Date(timeIntervalSince1970: Double(localDateInt))
            cell.dateLbl.text = date.toShortDateTimeString()
        }