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

Swift Nsdate Nsdateformatter Nsdatecomponents

Swift Problem Overview

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 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!)
}

I get the local time

> o/p: "12:52 PM"

But actual local time and output time difference is 23 minutes.

Swift Solutions

Solution 1 - Swift

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!!

Solution 2 - Swift

Mrugesh's answer is perfect, but if someone need to use their own formats, or in some different format, I've generalised it so you can give different format or same in both parameters.

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")

You can use it as above. Hope it helps.

Solution 3 - Swift

> 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")

Solution 4 - Swift

To convert a UTC Date to a local system date you could use the following Date extension:

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)
    }

}

Solution 5 - Swift

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: ...)

Solution 6 - Swift

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)

Solution 7 - Swift

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))
    }

Solution 8 - Swift

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()
        }

Content Type	Original Author	Original Content on Stackoverflow
Question	NiravS	View Question on Stackoverflow
Solution 1 - Swift	Mrugesh Tank	View Answer on Stackoverflow
Solution 2 - Swift	Hardik	View Answer on Stackoverflow
Solution 3 - Swift	Mandeep Singh	View Answer on Stackoverflow
Solution 4 - Swift	Jujuba	View Answer on Stackoverflow
Solution 5 - Swift	Bertrand Villain	View Answer on Stackoverflow
Solution 6 - Swift	Enamul Haque	View Answer on Stackoverflow
Solution 7 - Swift	javimuu	View Answer on Stackoverflow
Solution 8 - Swift	Dmih	View Answer on Stackoverflow