How do I get an ISO 8601 date on iOS?

Ios Problem Overview

It's easy enough to get the ISO 8601 date string (for example, 2004-02-12T15:19:21+00:00) in PHP via date('c'), but how does one get it in Objective-C (iPhone)? Is there a similarly short way to do it?

Here's the long way I found to do it:

NSDateFormatter* dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
dateFormatter.dateFormat = @"yyyy-MM-dd'T'HH:mm:ssZ";

NSDate *now = [NSDate date];
NSString *formattedDateString = [dateFormatter stringFromDate:now];
NSLog(@"ISO-8601 date: %@", formattedDateString);

// Output: ISO-8601 date: 2013-04-27T13:27:50-0700

It seems an awful lot of rigmarole for something so central.

Ios Solutions

Solution 1 - Ios

Use NSDateFormatter:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];   
NSLocale *enUSPOSIXLocale = [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"];
[dateFormatter setLocale:enUSPOSIXLocale];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ssZZZZZ"];
[dateFormatter setCalendar:[NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian]];

NSDate *now = [NSDate date];
NSString *iso8601String = [dateFormatter stringFromDate:now];

And in Swift:

let dateFormatter = DateFormatter()
let enUSPosixLocale = Locale(identifier: "en_US_POSIX")
dateFormatter.locale = enUSPosixLocale
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
dateFormatter.calendar = Calendar(identifier: .gregorian)

let iso8601String = dateFormatter.string(from: Date())

Solution 2 - Ios

iOS 10 introduces a new NSISO8601DateFormatter class to handle just this. If you're using Swift 3, your code would be something like this:

let formatter = ISO8601DateFormatter()
let date = formatter.date(from: "2016-08-26T12:39:00Z")
let string = formatter.string(from: Date())

Solution 3 - Ios

As a complement to maddy's answer, the time zone format should be "ZZZZZ" (5 times Z) for ISO 8601 instead of a single "Z" (which is for RFC 822 format). At least on iOS 6.

(see http://www.unicode.org/reports/tr35/tr35-25.html#Date_Format_Patterns)

Solution 4 - Ios

An often overlooked issue is that strings in ISO 8601 format might have milliseconds and might not.

In other words, both "2016-12-31T23:59:59.9999999" and "2016-12-01T00:00:00" are legit, but if you are using static-typed date formatter, one of them won't be parsed.

Starting from iOS 10 you should use ISO8601DateFormatter that handles all variations of ISO 8601 date strings. See example below:

let date = Date()
var string: String
 
let formatter = ISO8601DateFormatter()
string = formatter.string(from: date)
 
let GMT = TimeZone(abbreviation: "GMT")
let options: ISO8601DateFormatOptions = [.withInternetDateTime, .withDashSeparatorInDate, .withColonSeparatorInTime, .withTimeZone]
string = ISO8601DateFormatter.string(from: date, timeZone: GMT, formatOptions: options)

For iOS 9 and below use the following approach with multiple data formatters.

I haven't found an answer that covers both cases and abstracts away this subtle difference. Here is the solution that addresses it:

extension DateFormatter {
    
    static let iso8601DateFormatter: DateFormatter = {
        let enUSPOSIXLocale = Locale(identifier: "en_US_POSIX")
        let iso8601DateFormatter = DateFormatter()
        iso8601DateFormatter.locale = enUSPOSIXLocale
        iso8601DateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
        iso8601DateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
        return iso8601DateFormatter
    }()
    
    static let iso8601WithoutMillisecondsDateFormatter: DateFormatter = {
        let enUSPOSIXLocale = Locale(identifier: "en_US_POSIX")
        let iso8601DateFormatter = DateFormatter()
        iso8601DateFormatter.locale = enUSPOSIXLocale
        iso8601DateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss'Z'"
        iso8601DateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
        return iso8601DateFormatter
    }()
    
    static func date(fromISO8601String string: String) -> Date? {
        if let dateWithMilliseconds = iso8601DateFormatter.date(from: string) {
            return dateWithMilliseconds
        }
        
        if let dateWithoutMilliseconds = iso8601WithoutMillisecondsDateFormatter.date(from: string) {
            return dateWithoutMilliseconds
        }
        
        return nil
    }
}

Usage:

let dateToString = "2016-12-31T23:59:59.9999999"
let dateTo = DateFormatter.date(fromISO8601String: dateToString)
// dateTo: 2016-12-31 23:59:59 +0000

let dateFromString = "2016-12-01T00:00:00"
let dateFrom = DateFormatter.date(fromISO8601String: dateFromString)
// dateFrom: 2016-12-01 00:00:00 +0000

I also recommend checking Apple article about date formatters.

Solution 5 - Ios

So use Sam Soffee's category on NSDate found here. With that code added to your project, you can from then on use a single method on NSDate:

- (NSString *)sam_ISO8601String

Not only is it one line, its much faster than the NSDateFormatter approach, since its written in pure C.

Solution 6 - Ios

Update

From iOS 10, you can just use NSISO8601DateFormatter from Foundation

Original answer

From IS8601, the problems are the representation and time zone

ISO 8601 = year-month-day time timezone
For date and time, there are basic (YYYYMMDD, hhmmss, ...) and extended format (YYYY-MM-DD, hh:mm:ss, ...)
Time zone can be Zulu, offset or GMT
Separator for date and time can be space, or T
There are week format for date, but it is rarely used
Timezone can be a lot of spaces after
Second is optional

Here are some valid strings

2016-04-08T10:25:30Z
2016-04-08 11:25:30+0100
2016-04-08 202530GMT+1000
20160408 08:25:30-02:00
2016-04-08 11:25:30     +0100

Solutions

Parse step by step, like soffes ISO8601
Convert to basic format, like onmyway133 ISO8601

NSDateFormatter

So here is the format that I'm using in onmyway133 ISO8601

let formatter = NSDateFormatter()
formatter.locale = NSLocale(localeIdentifier: "en_US_POSIX")
formatter.dateFormat = "yyyyMMdd HHmmssZ"

About the Z identifier Date Field Symbol Table

Z: The ISO8601 basic format with hours, minutes and optional seconds fields. The format is equivalent to RFC 822 zone format (when optional seconds field is absent)

About locale Formatting Data Using the Locale Settings

> Locales represent the formatting choices for a particular user, not the user’s preferred language. These are often the same but can be different. For example, a native English speaker who lives in Germany might select English as the language and Germany as the region

About en_US_POSIX Technical Q&A QA1480 NSDateFormatter and Internet Dates

> On the other hand, if you're working with fixed-format dates, you should first set the locale of the date formatter to something appropriate for your fixed format. In most cases the best locale to choose is "en_US_POSIX", a locale that's specifically designed to yield US English results regardless of both user and system preferences. "en_US_POSIX" is also invariant in time (if the US, at some point in the future, changes the way it formats dates, "en_US" will change to reflect the new behaviour, but "en_US_POSIX" will not), and between machines ("en_US_POSIX" works the same on iOS as it does on OS X, and as it it does on other platforms).

Interesting related quetions

Solution 7 - Ios

Just use NSISO8601DateFormatter from Foundation framework.

let isoDateFormatter = ISO8601DateFormatter()
print("ISO8601 string: \(isoDateFormatter.string(from: Date()))")
// ISO8601 string: 2018-03-21T19:11:46Z

https://developer.apple.com/documentation/foundation/nsiso8601dateformatter?language=objc

Solution 8 - Ios

Based on this gist: https://github.com/justinmakaila/NSDate-ISO-8601/blob/master/NSDateISO8601.swift, the following method can be used to convert NSDate to ISO 8601 date string in the format of yyyy-MM-dd'T'HH:mm:ss.SSSZ

-(NSString *)getISO8601String
    {
        static NSDateFormatter *formatter = nil;
        if (!formatter)
        {
            formatter = [[NSDateFormatter alloc] init];
            [formatter setLocale: [NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"]];
            formatter.timeZone = [NSTimeZone timeZoneWithAbbreviation: @"UTC"];
            [formatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss.SSS"];
            
        }
        NSString *iso8601String = [formatter stringFromDate: self];
        return [iso8601String stringByAppendingString: @"Z"];
    }

Solution 9 - Ios

With iOS 15 you get ISO860 as follows:

let iso8601String = Date.now.ISO8601Format()

Solution 10 - Ios

If you are here because of a search result of the opposite way, here's the easiest solution:

let date = ISO8601DateFormatter().date(from: dateString)

Solution 11 - Ios

This is a little bit simpler and puts the date into UTC.

extension NSDate
{
    func iso8601() -> String
    {
        let dateFormatter = NSDateFormatter()
        dateFormatter.timeZone = NSTimeZone(name: "UTC")
        let iso8601String = dateFormatter.stringFromDate(NSDate())
        return iso8601String
    }
}

let date = NSDate().iso8601()

Solution 12 - Ios

Using Swift 3.0 and iOS 9.0

extension Date {
    private static let jsonDateFormatter: DateFormatter = {
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ"
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.timeZone = TimeZone(identifier: "UTC")!
        return formatter
    }()
    
    var IOS8601String: String {
        get {
            return Date.jsonDateFormatter.string(from: self)
        }
    }
    
    init?(fromIOS8601 dateString: String) {
        if let d = Date.jsonDateFormatter.date(from: dateString) {
            self.init(timeInterval: 0, since:d)
        } else {
            return nil
        }
    }
}

Content Type	Original Author	Original Content on Stackoverflow
Question	JohnK	View Question on Stackoverflow
Solution 1 - Ios	rmaddy	View Answer on Stackoverflow
Solution 2 - Ios	TwoStraws	View Answer on Stackoverflow
Solution 3 - Ios	Etienne	View Answer on Stackoverflow
Solution 4 - Ios	Vadim Bulavin	View Answer on Stackoverflow
Solution 5 - Ios	David H	View Answer on Stackoverflow
Solution 6 - Ios	onmyway133	View Answer on Stackoverflow
Solution 7 - Ios	LLIAJLbHOu	View Answer on Stackoverflow
Solution 8 - Ios	Zack Zhu	View Answer on Stackoverflow
Solution 9 - Ios	Abdullah Umer	View Answer on Stackoverflow
Solution 10 - Ios	Display Name	View Answer on Stackoverflow
Solution 11 - Ios	iphaaw	View Answer on Stackoverflow
Solution 12 - Ios	Denis Krivitski	View Answer on Stackoverflow