I have an ISO-8601 date string like this: "2017-02-07T00:00:00-08:00".
How can I extract the TimeZone object from this date?
Unfortunately, DateFormatter is no help since you don't want a Date nor does it provide any information about any timezone info about a parsed date string. And TimeZone doesn't have any initializer that can parse a timezone offset string.
So you will have to do the work yourself. Since you have a fixed format date string, you know the timezone offset is always going to be the last 6 characters of the string. The last 2 of those are the number of minutes and the first 3 of those are the number of hours (including the sign).
Extract these two substrings (hours and minutes) from the date string. Convert them both to Int. Then do some simple math to calculate an offset in seconds (hours * 3600 + minutes * 60).
Once you have that offset in seconds, you can create a TimeZone instance using the init(secondsFromGMT:) initializer.
Using rmaddys proposed solution, I wrote an extension for TimeZone which should do the job.
extension TimeZone {
init?(iso8601String: String) {
let timeZoneString = String(iso8601String.suffix(6))
let sign = String(timeZoneString.prefix(1))
guard sign == "+" || sign == "-" else {
return nil
}
let fullTimeString = timeZoneString.filter("0123456789".contains)
guard fullTimeString.count == 4 else {
return nil
}
guard let hours = Int(sign+fullTimeString.prefix(2)), let minutes = Int(sign+fullTimeString.suffix(2)) else {
return nil
}
let secondsFromGMT = hours * 3600 + minutes * 60
self.init(secondsFromGMT: secondsFromGMT)
}
}
You could create a date formatter that only returns the time zone such as below. Change the abbreviation to whichever time zone you are looking for.
let timeZoneOnlyDateFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.timeZone = TimeZone(abbreviation: "UTC")
formatter.dateStyle = .none
formatter.timeStyle = .none
return formatter
}()
And use these functions to convert it to a string or convert your string to a date.
func formatDateIntoString(date: Date, dateFormatter: DateFormatter) -> String {
return dateFormatter.string(from: date)
}
func formatStringIntoDate(string: String, dateFormatter: DateFormatter) -> Date! {
return dateFormatter.date(from: string)
}
Related
I'm using this extension to convert a string containing date to Date() object:
extension String {
func toDate() -> Date?{
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd/MM/YYYY"
let date = dateFormatter.date(from: self)
return date
}
}
the result always containing a time in it. I'm curious where is the time coming from, why it is not all zero?
print("11/12/2021".toDate())
result is ->
2020-12-19 21:00:00 +0000
In the time that I run the code, it is showing 21:00:00, so why it is 21? I believe It is not related to my time because I run it at different times.
A Date object indicates an instant in time anywhere on the planet, independent of time zone.
A DateFormatter can convert a String to a Date (or a Date to a String, but ignore that for now). When it converts a String to a Date, it may make assumptions about the time of day if that is not included in the String. I believe it assumes that the time is midnight (00:00:00) in the date formatter's time zone. (And by the way, midnight is the starting point of a day, so midnight is zero hours/minutes/seconds into the day. Essentially midnight IS zeros for time.)
So when you call your String extension to convert "11/12/2021" to a Date, the extension creates a DateFormatter which defaults to the device time zone. It creates a Date assuming Midnight in the local time zone.
When you print that date, it gets displayed in GMT.
It looks like your format string has problems though. You're getting the wrong year and month. I think you must be using the wrong month or day string in your formatter. (I always have to look those up when I use them.)
Edit:
You likely want a format string of "MM-dd-yyyy"
(2-digit month, 2-digit day of month, and 4-digit year.)
Lower-case "m" or "mm" is minutes. Upper-case "Y" is for "week of year" based calendars, which you probably don't want.
Try this code:
func toDate() -> Date?{
let dateFormatter = DateFormatter()
let posixLocale = Locale(identifier: "en_US_POSIX")
dateFormatter.dateFormat = "MM-dd-yyyy"
dateFormatter.locale = posixLocale
let date = dateFormatter.date(from: self)
return date
}
}
And to use it:
let dateString = "12/11/2021"
let date = dateString.toDate()
print(date)
if let date = date {
let convertedDateString = DateFormatter.localizedString(from: date, dateStyle: .medium, timeStyle: .medium)
print(convertedDateString)
} else {
print("Can't convert \(dateString) to a date")
}
That displays "Dec 11, 2021 at 12:00:00 AM" in my US locale (US Date formatting.) Note that since I use the DateFormatter class method localizedString(from:dateStyle:timeStyle:) I see midnight as the displayed time (The time you get from a DateFormatter when you don't specify a time, but displayed in the local time zone.)
The answer is:
when we are converting a string to a Date Object the important part is the time zone that we are converting it to.
for example, if you convert your string date to a UTC time zone when you want to bring it back you have to set the time zone of the date to UTC.
let dateFormatter = DateFormatter()
dateFormatter.timeZone = TimeZone(identifier: "UTC")
so this is the reason why when we are printing the Date() object it is deferred from our string date.
extension String {
func toDate() -> Date?{
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "mm-dd-yyyy"
let date = dateFormatter.date(from: self)
return date
}
}
extension Date {
func toString() -> String {
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "mm-dd-yyyy"
return dateFormatter.string(from: self)
}
}
let stringDate = "01-12-2021"
let date = "01-12-2021".toDate()
let convertBack = date?.toString()
print("(\(stringDate)) -> (\(date!)) -> (\(convertBack!))")
and the result is:
(01-12-2021) -> (2021-01-11 21:01:00 +0000) -> (01-12-2021)
so at the end when we convert back the Date object it will be the same. because that 2 dateFormatter in the extensions are using the default time zone. and if you want to specify a specific time zone you have to declare it in converting from and to string together.
This question already has an answer here:
DateFormatter doesn't return date for "HH:mm:ss"
(1 answer)
Closed 2 years ago.
I am working on an app that initializes dates from strings returned from the backend. The dateString is returned using the following format: "2020-03-05T09:00:00+00:00"
The method I have to do the conversion is:
extension Date {
static func convertDate(_ dateString: String?) -> Date? {
guard let dateString = dateString else { return nil }
let dateFormatter = DateFormatter()
dateFormatter.setLocalizedDateFormatFromTemplate("yyyy-MM-dd'T'HH:mm:ssZZZZZ")
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
return dateFormatter.date(from: dateString)
}
}
Everything was working fine until someone reported that if the user switches off "24-Hour Time" in settings the method above returns nil.
What am I doing wrong?
Thank you
You're using a very standardized timestamp format, which allows you to take advantage of the ISO8601DateFormatter.
let dateString = "2020-03-05T09:00:00+00:00"
let df = ISO8601DateFormatter()
df.formatOptions = [.withInternetDateTime]
if let date = df.date(from: dateString) {
print(date) // 2020-03-05 09:00:00 +0000
}
If a machine (like your server) is generating the timestamp then it will (should) always be in zulu time (GMT) so you don't need to do anything beyond this. You could specify a time zone but there isn't a point since the string will always zero it out for you.
df.timeZone = TimeZone(secondsFromGMT: 0)
This string represents an absolute moment in time. If you need a relative moment in time, such as the local time from the source, you'll need to identify that time zone and apply it here, which is also very straighforward.
I have 2 dates. I don't care about the date portion, just the time.
How can I compare 2 dates and get the timeinterval between 2 dates?
Should I set the dates to 01-01-2000 and leave the time alone to compare?
Use DateComponents and get the hour, minute, and second of the two dates. At this point you have to assume a full 24 hour, 86400 seconds per day. There's no need to worry about daylight saving or leap seconds or anything since you are doing date independent calculations.
Convert the hours, minutes, and seconds into total seconds of the day for the two dates. Then simply subtract the two totals and you have the difference.
Here's a helpful Date extension:
extension Date {
func secondsSinceMidnight() -> TimeInterval {
let comps = Calendar.current.dateComponents([.hour,.minute,.second], from: self)
return TimeInterval(comps.hour! * 3600 + comps.minute! * 60 + comps.second!)
}
func timeDifference(to date: Date) -> TimeInterval {
return date.secondsSinceMidnight() - self.secondsSinceMidnight()
}
}
Call timeDifference(to:) using your two dates and you will get the difference in seconds ignoring the date portion of the dates.
A negative result means that the to date is closer to midnight.
This is an alternative to rmaddy's solution completely based on DateComponents
extension Date {
func timeComponents() -> DateComponents {
return Calendar.current.dateComponents([.hour,.minute,.second], from: self)
}
func timeDifference(to date: Date) -> Int {
return Calendar.current.dateComponents([.second], from: date.timeComponents(), to: self.timeComponents()).second!
}
}
If you have two dates you can use the method timeIntervalSince(Date).
For instance:
func calculateElapsedTime(from someTime: Date) -> TimeInterval {
let currentTime = Date()
var elapsedTime = currentTime.timeIntervalSince(someTime)
return elapsedTime
}
If you only want to consider the time difference between the two dates, you first have to normalize the date. This can be done in the following cumbersome way:
let currentDate = Date()
let anotherDate = Date(timeInterval: 60, since: currentDate)
let formatter = DateFormatter()
formatter.timeStyle = .short
let currentTime = formatter.string(from: currentDate)
let anotherTime = formatter.string(from: anotherDate)
let currentIntervalTime = formatter.date(from: currentTime)
let anotherIntervalTime = formatter.date(from: anotherTime)
let elapsedTime = anotherIntervalTime?.timeIntervalSince(currentIntervalTime!)
I am taking the current time, in UTC, and putting it in nanaoseconds and then I need to take the nanoseconds and go back to a date in local time.
I am able to do get the time to nanoseconds and then back to a date string but the time gets convoluted when I go from a string to date.
//Date to milliseconds
func currentTimeInMiliseconds() -> Int! {
let currentDate = NSDate()
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = format
dateFormatter.timeZone = NSTimeZone(name: "UTC") as TimeZone!
let date = dateFormatter.date(from: dateFormatter.string(from: currentDate as Date))
let nowDouble = date!.timeIntervalSince1970
return Int(nowDouble*1000)
}
//Milliseconds to date
extension Int {
func dateFromMilliseconds(format:String) -> Date {
let date : NSDate! = NSDate(timeIntervalSince1970:Double(self) / 1000.0)
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = format
dateFormatter.timeZone = TimeZone.current
let timeStamp = dateFormatter.string(from: date as Date)
let formatter = DateFormatter()
formatter.dateFormat = format
return ( formatter.date( from: timeStamp ) )!
}
}
The timestamp is correct but the date returned isn't.
I don't understand why you're doing anything with strings...
extension Date {
var millisecondsSince1970:Int64 {
Int64((self.timeIntervalSince1970 * 1000.0).rounded())
}
init(milliseconds:Int64) {
self = Date(timeIntervalSince1970: TimeInterval(milliseconds) / 1000)
}
}
Date().millisecondsSince1970 // 1476889390939
Date(milliseconds: 0) // "Dec 31, 1969, 4:00 PM" (PDT variant of 1970 UTC)
As #Travis Solution works but in some cases
var millisecondsSince1970:Int WILL CAUSE CRASH APPLICATION ,
with error
Double value cannot be converted to Int because the result would be greater than Int.max if it occurs Please update your answer with Int64
Here is Updated Answer
extension Date {
var millisecondsSince1970:Int64 {
return Int64((self.timeIntervalSince1970 * 1000.0).rounded())
//RESOLVED CRASH HERE
}
init(milliseconds:Int) {
self = Date(timeIntervalSince1970: TimeInterval(milliseconds / 1000))
}
}
About Int definitions.
On 32-bit platforms, Int is the same size as Int32, and on 64-bit platforms, Int is the same size as Int64.
Generally, I encounter this problem in iPhone 5, which runs in 32-bit env. New devices run 64-bit env now. Their Int will be Int64.
Hope it is helpful to someone who also has same problem
#Travis solution is right, but it loses milliseconds when a Date is generated. I have added a line to include the milliseconds into the date:
If you don't need this precision, use the Travis solution because it will be faster.
extension Date {
func toMillis() -> Int64! {
return Int64(self.timeIntervalSince1970 * 1000)
}
init(millis: Int64) {
self = Date(timeIntervalSince1970: TimeInterval(millis / 1000))
self.addTimeInterval(TimeInterval(Double(millis % 1000) / 1000 ))
}
}
//Date to milliseconds
func currentTimeInMiliseconds() -> Int {
let currentDate = Date()
let since1970 = currentDate.timeIntervalSince1970
return Int(since1970 * 1000)
}
//Milliseconds to date
extension Int {
func dateFromMilliseconds() -> Date {
return Date(timeIntervalSince1970: TimeInterval(self)/1000)
}
}
I removed seemingly useless conversion via string and all those random !.
let dateTimeStamp = NSDate(timeIntervalSince1970:Double(currentTimeInMiliseconds())/1000) //UTC time //YOUR currentTimeInMiliseconds METHOD
let dateFormatter = NSDateFormatter()
dateFormatter.timeZone = NSTimeZone.localTimeZone()
dateFormatter.dateFormat = "yyyy-MM-dd"
dateFormatter.dateStyle = NSDateFormatterStyle.FullStyle
dateFormatter.timeStyle = NSDateFormatterStyle.ShortStyle
let strDateSelect = dateFormatter.stringFromDate(dateTimeStamp)
print("Local Time", strDateSelect) //Local time
let dateFormatter2 = NSDateFormatter()
dateFormatter2.timeZone = NSTimeZone(name: "UTC") as NSTimeZone!
dateFormatter2.dateFormat = "yyyy-MM-dd"
let date3 = dateFormatter.dateFromString(strDateSelect)
print("DATE",date3)
#Prashant Tukadiya answer works. But if you want to save the value in UserDefaults and then compare it to other date you get yout int64 truncated so it can cause problems. I found a solution.
Swift 4:
You can save int64 as string in UserDefaults:
let value: String(Date().millisecondsSince1970)
let stringValue = String(value)
UserDefaults.standard.set(stringValue, forKey: "int64String")
Like that you avoid Int truncation.
And then you can recover the original value:
let int64String = UserDefaults.standard.string(forKey: "int64String")
let originalValue = Int64(int64String!)
This allow you to compare it with other date values:
let currentTime = Date().millisecondsSince1970
let int64String = UserDefaults.standard.string(forKey: "int64String")
let originalValue = Int64(int64String!) ?? 0
if currentTime < originalValue {
return false
} else {
return true
}
Hope this helps someone who has same problem
Heres a simple solution in Swift 5/iOS 13.
extension Date {
func toMilliseconds() -> Int64 {
Int64(self.timeIntervalSince1970 * 1000)
}
init(milliseconds:Int) {
self = Date().advanced(by: TimeInterval(integerLiteral: Int64(milliseconds / 1000)))
}
}
This however assumes you have calculated the difference between UTF time and local time and adjusted and accounted for in the milliseconds. For that look to calendar
var cal = Calendar.current
cal.timeZone = TimeZone(abbreviation: "UTC")!
let difference = cal.compare(dateGiven, to: date, toGranularity: .nanosecond)
Simple one-line code to get time token in UInt64
let time = UInt64(Date().timeIntervalSince1970 * 1000)
print(time) <----- prints time in UInt64
Additional tip:
For timestamp with 10 Digit milliseconds since 1970 for API call then
let timeStamp = Date().timeIntervalSince1970
print(timeStamp) <-- prints current time stamp
Watch out if you are going to compare dates after the conversion!
For instance, I got simulator's asset with date as TimeInterval(366144731.9), converted to milliseconds Int64(1344451931900) and back to TimeInterval(366144731.9000001), using
func convertToMilli(timeIntervalSince1970: TimeInterval) -> Int64 {
return Int64(timeIntervalSince1970 * 1000)
}
func convertMilliToDate(milliseconds: Int64) -> Date {
return Date(timeIntervalSince1970: (TimeInterval(milliseconds) / 1000))
}
I tried to fetch the asset by creationDate and it doesn't find the asset, as you could figure, the numbers are not the same.
I tried multiple solutions to reduce double's decimal precision, like round(interval*1000)/1000, use NSDecimalNumber, etc... with no success.
I ended up fetching by interval -1 < creationDate < interval + 1, instead of creationDate == Interval.
There may be a better solution!?
Unless you absolutely have to convert the date to an integer, consider using a Double instead to represent the time interval. After all, this is the type that timeIntervalSince1970 returns. All of the answers that convert to integers loose sub-millisecond precision, but this solution is much more accurate (although you will still lose some precision due to floating-point imprecision).
public extension Date {
/// The interval, in milliseconds, between the date value and
/// 00:00:00 UTC on 1 January 1970.
/// Equivalent to `self.timeIntervalSince1970 * 1000`.
var millisecondsSince1970: Double {
return self.timeIntervalSince1970 * 1000
}
/**
Creates a date value initialized relative to 00:00:00 UTC
on 1 January 1970 by a given number of **milliseconds**.
equivalent to
```
self.init(timeIntervalSince1970: TimeInterval(milliseconds) / 1000)
```
- Parameter millisecondsSince1970: A time interval in milliseconds.
*/
init(millisecondsSince1970 milliseconds: Double) {
self.init(timeIntervalSince1970: TimeInterval(milliseconds) / 1000)
}
}
I'm pretty new to swift (and programming altogether). I'm trying to convert an Int into a String. I've tried using switch statements but every time I use them, it never changes to the String (AKA it prints the number 4) An example of what I'm trying to do is as follows:
class Birthday(_ month: Int, _ day:Int, _ year:Int) -> String{
//Here is where I'd like to turn my month into April
Return (month)
}
let example = Birthday()
example(4,15,1988)
If you really just want to get a month name from a month number, you can do the following:
let formatter = DateFormatter()
let monthName = formatter.monthSymbols[month - 1] // Assuming 1 means January
But since you are passing in a month, day, and year, you presumably want to create a Date and then you want to format that Date into a `String.
Create a Date using Calendar and DateComponents.
let date = Calendar.current.date(from: DateComponents(year: year, month: month, day: day))
Then you format the Date into a String using DateFormatter.
let formatter = DateFormatter()
formatter.dateStyle = .long // choose a desired style
formatter.timeStyle = .none
let string = formatter.string(from: date)
You can use a dictionary which maps objects to each other. For example, a months dictionary could look like:
let months: [Int:String] = [1:"January", 2:"February",...]
return months[4] // returns "April"
Simple solution to get you started would be a method that takes an integer and return your month string.
func numberToMonth(number: Int) -> String {
guard number > 0, number < 13 else { return "" }
return DateFormatter().monthSymbols[number-1]
}