Get UTC time and local time from NSDate object

In objective-c, the following code results in the UTC date time information using the date API.

date

NSDate *currentUTCDate = [NSDate date]


In Swift however,

let date = NSDate.date()


results in local date and time.

I have two questions:

date

NSDate

NSDate

EDIT 1: Thanks for all the inputs but I am not looking for NSDateFormatter objects or string values. I am simply looking for NSDate objects (however we cook them up but that's the requirement).
See point 1.

NSDateFormatter

NSDate

NSDate

NSDate

9 Answers
9

The documentation says that the date method returns a new date set to the current date and time regardless of the language used.

date

The issue probably sits somewhere where you present the date using NSDateFormatter. NSDate is just a point on a time line. There is no time zones when talking about NSDate. I made a test.

NSDateFormatter

NSDate

NSDate

print(NSDate())


Output: 2014-07-23 17:56:45 +0000

2014-07-23 17:56:45 +0000

NSLog(@"%@", [NSDate date]);


Output: 2014-07-23 17:58:15 +0000

2014-07-23 17:58:15 +0000

Result - No difference.

let x = NSDate.date()

description

NSDate

2014-07-23 16:56:45 +0000

2014-07-23 17:56:45 +0000

2014-07-23 16:56:45 +0000

2014-07-23 17:56:45 +0100

+0100

NSDate is a specific point in time without a time zone. Think of it as the number of seconds that have passed since a reference date. How many seconds have passed in one time zone vs. another since a particular reference date? The answer is the same.

NSDate

Depending on how you output that date (including looking at the debugger), you may get an answer in a different time zone.

If they ran at the same moment, the values of these are the same. They're both the number of seconds since the reference date, which may be formatted on output to UTC or local time. Within the date variable, they're both UTC.

Objective-C:

NSDate *UTCDate = [NSDate date]


Swift:

let UTCDate = NSDate.date()


To explain this, we can use a NSDateFormatter in a playground:

import UIKit

let date = NSDate.date()
// "Jul 23, 2014, 11:01 AM" <-- looks local without seconds. But:

var formatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZ"
let defaultTimeZoneStr = formatter.stringFromDate(date)
// "2014-07-23 11:01:35 -0700" <-- same date, local, but with seconds
formatter.timeZone = NSTimeZone(abbreviation: "UTC")
let utcTimeZoneStr = formatter.stringFromDate(date)
// "2014-07-23 18:01:41 +0000" <-- same date, now in UTC


The date output varies, but the date is constant. This is exactly what you're saying. There's no such thing as a local NSDate.

As for how to get microseconds out, you can use this (put it at the bottom of the same playground):

let seconds = date.timeIntervalSince1970
let microseconds = Int(seconds * 1000) % 1000 // chops off seconds


To compare two dates, you can use date.compare(otherDate).

date.compare(otherDate)

po

NSDate

NSFormatter

dateA.compare(dateB);

Xcode 9 • Swift 4 (also works Swift 3.x)

extension Formatter
// create static date formatters for your date representations
static let preciseLocalTime: DateFormatter =
let formatter = DateFormatter()
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.dateFormat = "HH:mm:ss.SSS"
return formatter
()
static let preciseGMTTime: DateFormatter =
let formatter = DateFormatter()
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = TimeZone(secondsFromGMT: 0)
formatter.dateFormat = "HH:mm:ss.SSS"
return formatter
()



extension Date
// you can create a read-only computed property to return just the nanoseconds from your date time
var nanosecond: Int return Calendar.current.component(.nanosecond, from: self)
// the same for your local time
var preciseLocalTime: String
return Formatter.preciseLocalTime.string(for: self) ?? ""

// or GMT time
var preciseGMTTime: String
return Formatter.preciseGMTTime.string(for: self) ?? ""




Playground testing

Date().preciseLocalTime // "09:13:17.385" GMT-3
Date().preciseGMTTime // "12:13:17.386" GMT
Date().nanosecond // 386268973


This might help you also formatting your dates:

a date is independant of any timezone, so use a Dateformatter and attach a timezone for display:

swift:

let date = NSDate()
let dateFormatter = NSDateFormatter()
let timeZone = NSTimeZone(name: "UTC")

dateFormatter.timeZone = timeZone

println(dateFormatter.stringFromDate(date))


objC:

NSDate *date = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"UTC"];

[dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
[dateFormatter setDateStyle:NSDateFormatterMediumStyle];
[dateFormatter setTimeZone:timeZone];
NSLog(@"%@", [dateFormatter stringFromDate:date]);


Xcode 9 • Swift 4 or Swift 3:

let date = Date() // default is UTC.


This code gives date in UTC. If you need the local time, you should call the following extension with timezone as Timezone.current

Timezone.current

extension Date

var currentUTCTimeZoneDate: String
let formatter = DateFormatter()
formatter.timeZone = TimeZone(identifier: "UTC")
formatter.amSymbol = "AM"
formatter.pmSymbol = "PM"
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

return formatter.string(from: self)




For UTC time, use it like: Date().currentUTCTimeZoneDate

Date().currentUTCTimeZoneDate

At the moment (with the latest changes to Swift), NSDate.date() is not longer available.

NSDate.date()

Instead you just need to initialize NSDate and it gets the current date and time.

To try it, in a playground:

NSDate

var d = NSDate()
d


and you will get:

Oct 22, 2014, 12:20 PM"


Swift 3

You can get Date based on your current timezone from UTC

extension Date
func currentTimeZoneDate() -> String
let dtf = DateFormatter()
dtf.timeZone = TimeZone.current
dtf.dateFormat = "yyyy-MM-dd HH:mm:ss"

return dtf.string(from: self)




Call like this:

Date().currentTimeZoneDate()


My Xcode Version 6.1.1 (6A2008a)

In playground, test like this:

// I'm in East Timezone 8
let x = NSDate() //Output:"Dec 29, 2014, 11:37 AM"
let y = NSDate.init() //Output:"Dec 29, 2014, 11:37 AM"
println(x) //Output:"2014-12-29 03:37:24 +0000"


// seconds since 2001
x.hash //Output:441,517,044
x.hashValue //Output:441,517,044
x.timeIntervalSinceReferenceDate //Output:441,517,044.875367

// seconds since 1970
x.timeIntervalSince1970 //Output:1,419,824,244.87537


I found an easier way to get UTC in Swift4. Put this code in playground

let date = Date()
//"Mar 15, 2018 at 4:01 PM"

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZ"
dateFormatter.timeZone = TimeZone(secondsFromGMT: 0)

let newDate = dateFormatter.string(from: date)
//"2018-03-15 21:05:04 +0000"

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