Converting UTC date format to local nsdate

问题:

I am getting from my server a string date in UTC time zone and I need to convert it to the local time zone.

MY CODE:

let utcTime = "2015-04-01T11:42:00.269Z"    
let dateFormatter = NSDateFormatter()
dateFormatter.timeZone = NSTimeZone(name: "UTC")
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
let date = dateFormatter.dateFromString(utcTime)
println("utc: \(utcTime), date: \(date)")

this prints -

utc: 2015-04-01T11:42:00.269Z, date: Optional(2015-04-01 11:42:00 +0000)

if I remove

dateFormatter.timeZone = NSTimeZone(name: "UTC") 

it prints

utc: 2015-04-01T11:42:00.269Z, date: Optional(2015-04-01 08:42:00 +0000)

my local time zone is UTC +3 and in the first option I get UTC in the second option I get UTC -3

I should get

utc: 2015-04-01T11:42:00.269Z, date: Optional(2015-04-01 14:42:00 +0000)

So how do I convert the UTC date format to local time?

回答1:

Something along the following worked for me in Objective-C :

// create dateFormatter with UTC time format
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss"]; 
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
NSDate *date = [dateFormatter dateFromString:@"2015-04-01T11:42:00"]; // create date from string

// change to a readable time format and change to local time zone
[dateFormatter setDateFormat:@"EEE, MMM d, yyyy - h:mm a"];
[dateFormatter setTimeZone:[NSTimeZone localTimeZone]];
NSString *timestamp = [dateFormatter stringFromDate:date];

I keep these two websites handy for converting different time formats: http://www.w3.org/TR/NOTE-datetime

http://benscheirman.com/2010/06/dealing-with-dates-time-zones-in-objective-c/

In Swift it will be:

// create dateFormatter with UTC time format
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
dateFormatter.timeZone = NSTimeZone(name: "UTC")
let date = dateFormatter.dateFromString("2015-04-01T11:42:00")// create   date from string

// change to a readable time format and change to local time zone
dateFormatter.dateFormat = "EEE, MMM d, yyyy - h:mm a"
dateFormatter.timeZone = NSTimeZone.localTimeZone()
let timeStamp = dateFormatter.stringFromDate(date!)

回答2:

Swift version of c_rath answer:

// create dateFormatter with UTC time format
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
dateFormatter.timeZone = NSTimeZone(name: "UTC")
let date = dateFormatter.dateFromString("2015-04-01T11:42:00")

// change to a readable time format and change to local time zone
dateFormatter.dateFormat = "EEE, MMM d, yyyy - h:mm a"
dateFormatter.timeZone = NSTimeZone.localTimeZone() 
let timeStamp = dateFormatter.stringFromDate(date!)

回答3:

Try this Swift extension

Swift 4: UTC/GMT ⟺ Local (Current/System)

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 {
        let timezone = TimeZone.current
        let seconds = TimeInterval(timezone.secondsFromGMT(for: self))
        return Date(timeInterval: seconds, since: self)
    }

}


// Try it
let utcDate = Date().toGlobalTime()
let localDate = utcDate.toLocalTime()

print("utcDate - (utcDate)")
print("localDate - (localDate)")

回答4:

In Swift 3 this works well:

// create dateFormatter with UTC time format
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
let date = dateFormatter.date(from: "2015-04-01T11:42:00")// create date from string

// change to a readable time format and change to local time zone
dateFormatter.dateFormat = "EEE, MMM d, yyyy - h:mm a"
dateFormatter.timeZone = TimeZone.current
let timeStamp = dateFormatter.string(from: date!)

回答5:

Expanding on what others have mentioned, here is a handy NSDate extension in Swift

import Foundation

extension NSDate {
    func ToLocalStringWithFormat(dateFormat: String) -> String {
        // change to a readable time format and change to local time zone
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = dateFormat
        dateFormatter.timeZone = NSTimeZone.localTimeZone()
        let timeStamp = dateFormatter.stringFromDate(self)

        return timeStamp
    }
}

回答6:

Maybe you can try something like:

extension NSDate {
    convenience init(utcDate:String, dateFormat:String="yyyy-MM-dd HH:mm:ss.SSS+00:00") {
        // 2016-06-06 00:24:21.164493+00:00
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = dateFormat
        dateFormatter.timeZone = NSTimeZone(name: "UTC")

        let date = dateFormatter.dateFromString(utcDate)!
        let s = NSTimeZone.localTimeZone().secondsFromGMTForDate(date)
        let timeInterval = NSTimeInterval(s)

        self.init(timeInterval: timeInterval, sinceDate:date)
    }
}

回答7:

I had to remove both z and milli seconds from c_rath solution. Works in swift 4.

extension String {
    func fromUTCToLocalDateTime() -> String {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
        dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
        var formattedString = self.replacingOccurrences(of: "Z", with: "")
        if let lowerBound = formattedString.range(of: ".")?.lowerBound {
            formattedString = "\(formattedString[..<lowerBound])"
        }

        guard let date = dateFormatter.date(from: formattedString) else {
            return self
        }

        dateFormatter.dateFormat = "EEE, MMM d, yyyy - h:mm a"
        dateFormatter.timeZone = TimeZone.current
        return dateFormatter.string(from: date)
    }
}