I copied an extension for Swift's Date object somewhere that allows me to initialize a Date from a string as follows:
extension Date {
init(fromString: String) {
let str = "\(fromString) 12:00"
let dateStringFormatter = DateFormatter()
dateStringFormatter.dateFormat = "yyyy-MM-dd hh:mm"
dateStringFormatter.timeZone = NSTimeZone.default
let d = dateStringFormatter.date(from: str)!
self.init(timeInterval: 0, since: d)
}
}
If, for instance, I pass "2016-10-16" as string for the custom initializer, the Date, when printed, should be "2016-10-16 22:00:00 +0000", but right now it is: "2016-10-15 22:00:00 +0000".
Any idea why?
Thanks!
Resolved the issue thanks to #jcaron.
Problem
The problem was that I mixed up 12 and 24 hour fomat when doing "hh:mm". This is used for 12-hour formats while I wanted to use the 24-hour format.
Solution
To solve that, "hh:mm" needs to be changed to "HH:mm"
Related
In our app there is the issue with creating a date from string but is only reproducible with a very specific combination. Unfortunately, there is no way of getting it from the user that experienced the issue, so I decided to just go for it and try every possible combination:
import Foundation
var dateOnlyDateFormatter: (String, String) -> DateFormatter = { timeZoneS, localeS in
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd"
formatter.timeZone = TimeZone(identifier: timeZoneS)
formatter.locale = Locale(identifier: localeS)
return formatter
}
let date = "2022-05-27"
let time = "06:15"
for timeZone in TimeZone.knownTimeZoneIdentifiers {
for locale in Locale.availableIdentifiers {
let dateFormatter = dateOnlyDateFormatter(timeZone, locale)
let printDate = dateFormatter.date(from: date)
if printDate == nil {
print("TimeZone: \(timeZone), Locale: \(locale)")
}
}
}
The result:
TimeZone: America/Asuncion, Locale: ar_SA
TimeZone: America/Asuncion, Locale: en_SA
I am not too sure what is the best way to handle this issue. Obviously our BE could return date using one specific Locale, like en_US_POSIX, but I have very little control over that, being a part of a much bigger older system. Has anybody experienced an issue like that?
If you read the "Working With Fixed Format Date Representations" section of the DateFormatter docs, you'll find:
For most fixed formats, you should also set the locale property to a POSIX locale ("en_US_POSIX"), and set the timeZone property to UTC.
You should probably just follow the advice here... But here's possibly why SA and the Paraguay timezone produces nil.
Further down that section, there is a link to a technical Q&A where this is explained in more detail. The part that is most related to your problem is:
A user can change their calendar (using System Preferences > Language & Region > Calendar on OS X, or Settings > General > International > Calendar on iOS). In that case NSDateFormatter will treat the numbers in the string you parse as if they were in the user's chosen calendar. For example, if the user selects the Buddhist calendar, parsing the year "2010" will yield an NSDate in 1467, because the year 2010 on the Buddhist calendar was the year 1467 on the (Gregorian) calendar that we use day-to-day.
In the locale SA, the numbers of your date string seem to be interpreted using the Islamic Calendar. Take a look at today's date when formatted with en_SA and America/New_York.
let dateFormatter = dateOnlyDateFormatter("America/New_York", "en_SA")
let printDate = dateFormatter.string(from: .init())
print(printDate)
// 1443-10-26
Also take a look at the non-nil dates that is parsed by en_SA and America/New_York
let dateFormatter = dateOnlyDateFormatter("America/New_York", "en_SA")
let printDate = dateFormatter.date(from: date)
print(printDate)
// 2583-10-05 04:00:00 +0000
Notice that 10-05 is the first Sunday of the year 2583 (See this calendar). If Paraguay still uses the same DST rules as it does now in 2583, then it would mean that there is a DST gap transition at 2583-10-05 00:00:00, starting the DST period. The hour starting from 00:00:00 would be skipped, so 00:00:00 would not exist.
When parsing a date only, DateFormatter would try to set the time components to be 00:00:00 in the timezone of the formatter, but 00:00:00 does not exist, so the parsing fails.
In any case, just set locale to posix and timeZone to UTC when you have set dateFormat.
So if you use 'time' like this, there will be no nil values:
let dateOnlyDateFormatter: (String, String) -> DateFormatter = { timeZoneS, localeS in
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm"
formatter.timeZone = TimeZone(identifier: timeZoneS)
formatter.locale = Locale(identifier: localeS)
return formatter
}
let date = "2022-05-27 06:15"
//let time = "06:15"
for timeZone in TimeZone.knownTimeZoneIdentifiers {
for locale in Locale.availableIdentifiers {
let dateFormatter = dateOnlyDateFormatter(timeZone, locale)
let printDate = dateFormatter.date(from: date)
if printDate == nil {
print(">>>>>>>> TimeZone: \(timeZone), Locale: \(locale)")
} else {
print("..... \(printDate)")
}
}
}
I have a string coming from API and its format will be like this
"2021-03-01T15:00:00+07:00"
so i try to convert this string to date using this code
// string to date
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
let date = dateFormatter.date(from: isoDate)!
print("date from date Formatter = \(date)")
// convert date back to string
dateFormatter.dateFormat = "EEEE HH:mm"
let dateString = dateFormatter.string(from: date)
print("date string \(dateString)")
return dateString
The result that I expect is -> "2021-03-01 08:00:00 +0000", "Monday 15:00"
When I try this on playground the result is what I want, but when I try this on my project the result is
-> "1478-03-01 08:00:00 +0000", "Sunday 14:42"
How can I change the result to the same as i expect? Thanks
It looks like you are using a different calendar than you expect in your project (buddhist maybe?) and I guess this is because you haven't set one explicitly so it's the one set in System Preferences.
So if you for some reason do not want to use the users current calendar (and locale and time zone) you need to set those properties on your date formatter instance
//Gregorian calendar
dateFormatter.calendar = Calendar.init(identifier: .gregorian)
//UTC time zone
dateFormatter.timeZone = TimeZone(identifier: "UTC")
//English locale
dateFormatter.locale = Locale(identifier: "en_US_POSIX")
This will give you the expected output.
Note that the playground is a bit inconsequent in what it uses and it seems to be a mix of what we have set in our System preferences and hardcoded values.
I've watching trough stack overflow to find the answer and I can't find it I want to cast this string value "1900-01-01T00:00:00" to Date format, I was trying with some formats like those:
"yyyy-MM-dd HH:mm:ss"
"EEE, dd MMM yyyy hh:mm:ss +zzzz"
"YYYY-MM-dd HH:mm:ss.A"
"yyyy-MM-dd HH:mm:ss.S"
but anyone of those its working.
and I want the date format like this
"dd-mm-yyyy"
Hope you can help me!
Thanks.
It is a two step process, first converting 1900-01-01T00:00:00 (known as a RFC 3999 or ISO 8601 date, referred to the specifications that define this format) into a Date object, and then converting that Date object back to a string in the form of 01-01-1900:
To convert your string in the form of 1900-01-01T00:00:00 into a Date object, you can use ISO8601DateFormatter:
let formatter = ISO8601DateFormatter()
formatter.formatOptions.remove(.withTimeZone)
let date = formatter.date(from: string)!
That is equivalent to the following DateFormat, in which one has to manually set the locale to en_US_POSIX (because RFC 3999/ISO 8601 dates use a Gregorian calendar, regardless of what the device's default calendar type) and sets the timeZone to GMT/Zulu, because usually RFC 3999/ISO 8601 dates are representing GMT unless specified otherwise:
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = TimeZone(secondsFromGMT: 0)
let date = formatter.date(from: string)!
For more information about the importance of timezones and locales in parsing RFC 3999 and ISO 8601 dates, see Apple's Technical Q&A 1480.
Then, to convert that Date object to a string into 01-01-1900 (day, month, and year), you'd use a format string of dd-MM-yyyy (note the uppercase MM for "month", to distinguish it from mm for "minute"):
let formatter2 = DateFormatter()
formatter2.dateFormat = "dd-MM-yyyy"
let string = formatter2.string(from: date)
Two observations regarding the dateFormat string:
If this string is for displaying to the user, you might use use dateStyle rather than dateFormat, e.g.:
formatter2.dateStyle = .short
While this will generate a slightly different format, e.g. dd/MM/yy, the virtue of this approach is that the string will be localized (e.g. UK users will see MM/dd/yyyy, their preferred way of seeing short dates).
It just depends upon the purpose of your dd-MM-yyyy format. If it's for internal purposes, go ahead and use dateFormat. But if it's for showing dates in your UI, use dateStyle instead, and enjoy the localization that DateFormatter does automatically for you. For more information, see "Working With User-Visible Representations of Dates and Times" section of the DateFormatter reference.
Note that in the absence of a timeZone specified for this second formatter, it assumes that while the ISO 8601 date was in GMT, that you want to see the date in your local timezone. For example, (1900-01-01T00:00:00 GMT was Dec 31, 1899 at 4pm in California). If you want to see the date string of the original ISO 8601 object, not corrected for timezones, you'd just set the timeZone of this second formatter to be GMT as well, e.g.
formatter2.timeZone = TimeZone(secondsFromGMT: 0)
As others have pointed out, you want to avoid unnecessarily re-instantiating DateFormatter objects. So you might put these formatters in properties that are instantiated only once, or use an extension:
extension DateFormatter {
static let customInputFormatter: ISO8601DateFormatter = {
let formatter = ISO8601DateFormatter()
formatter.formatOptions.remove(.withTimeZone)
return formatter
}()
static let customOutputFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateFormat = "dd-MM-yyyy"
formatter.timeZone = TimeZone(secondsFromGMT: 0) // if you want date in your local timezone, remove this line
return formatter
}()
}
And then:
let input = "1900-01-01T00:00:00"
let date = DateFormatter.customInputFormatter.date(from: input)!
let output = DateFormatter.customOutputFormatter.string(from: date)
print(output)
This is how I do custom date formatters:
extension DateFormatter {
static let inDateFormatter: DateFormatter = {
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
return dateFormatter
}()
static let outDateFormatter: DateFormatter = {
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd-mm-yyyy"
return dateFormatter
}()
}
And then use it like:
if let date = DateFormatter.inDateFormatter.date(from: "1900-01-01T00:00:00") {
let newDateString = DateFormatter.outDateFormatter.string(from: date);
print(newDateString) //prints 01-00-1900
}
This avoids any potential performance issues and is clear at the point of use, while still being concise.
Use this extension I created, where you can pass the format as a parameter.
extension String
{
func toDate( dateFormat format : String) -> Date
{
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = format
if let date = dateFormatter.date(from: self)
{
return date
}
print("Invalid arguments ! Returning Current Date . ")
return Date()
}
}
"1900-01-01T00:00:00".toDate(dateFormat: "yyyy-MM-dd'T'HH:mm:ss") //Plyground call test
I want to get a date that is represented in a String with a time zone GMT+1 and display it on screen with the local time zone GMT+10.
I have 2 methods, one is for create a date from a String (with GMT+1 timeZone), the other one is to format the date into a String (with localTimeZone GMT+10):
func dateFromString(dateString: String) -> NSDate? {
let dateFormatter = NSDateFormatter()
dateFormatter.timeZone = NSTimeZone(abbreviation: "GMT+1")
dateFormatter.dateFormat = "M/d/yyyy hh:mma"
return dateFormatter.dateFromString(dateString)
}
func stringFromDate(date: NSDate) -> String {
let dateFormatter = NSDateFormatter()
dateFormatter.timeZone = NSTimeZone.localTimeZone()
dateFormatter.timeStyle = NSDateFormatterStyle.ShortStyle
return dateFormatter.stringFromDate(date)
}
In the playground, when I do this:
let date = dateFromString("4/8/2015 1:29am")!
println(date)
println(stringFromDate(date))
I get the following output on the right side:
"Apr 8, 2015, 1:29 AM"
"2015-04-07 15:29:00 +0000"
"1:29 AM"
I don't understand why I don't get what I am expecting and looking for:
"Apr 8, 2015, 1:29 AM"
"2015-04-08 10:29:00 +0000"
"10:29 AM"
What's wrong?
Input formatters need the time zone in their string. Like so:
func dateFromString(dateString: String) -> NSDate? {
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "M/d/yyyy hh:mma z"
return dateFormatter.dateFromString(dateString)
}
let date = dateFromString("4/8/2015 1:29am GMT+01")!
Also note that NSTimeZone names have a two digit offset. Compare in the playground
var oops = NSTimeZone(abbreviation: "GMT+1")
var righteous = NSTimeZone(abbreviation: "GMT+01")
The first is nil, the second is not.
I wouldn't trust the formatting of a time stamp that the debugger prints. In my experience dates are always in UTC regardless of the time zone you set according to the log. Try adding the date as a string to a label on the project and see if it's right.
The reasoning behind this as far as I know is that when you print to the log, all it's doing is calling -description. In the case of NSDate this will return in UTC by definition.
I'm working with some JSON data that returns a dateTime in this format: "2015-01-17T20:00Z", when I attempt to turn this into an NSDate object, I'm always left with nil. I've read through several of the tutorials and answers here on SO, Apple's NSDate / NSDateFormatter / Date Formatting docs, and pinged a few IRC channels.
Can anyone tell me what I'm doing wrong and a possible work around?
My failing code in a Swift playground:
let dateString = "2015-01-17T20:00Z"
let dateStringFormatter = NSDateFormatter()
dateStringFormatter.dateFormat = "yyyy-MM-ddThh:mmZ"
let d = dateStringFormatter.dateFromString(dateString)
println(d)
Output: "Optional(2015-01-17 06:00:00 +0000)"
Working code in the same Swift playground:
let dateString = "2015-01-17"
let dateStringFormatter = NSDateFormatter()
dateStringFormatter.dateFormat = "yyyy-MM-dd"
let d = dateStringFormatter.dateFromString(dateString)
println(d)
Output: "nil"
You have to format it like this "yyyy-MM-dd\'T\'HH:mmZ". You can try it also with this extension:
extension String {
func toDateFormattedWith(format:String)-> NSDate {
let formatter = NSDateFormatter()
formatter.dateFormat = format
return formatter.dateFromString(self)!
}
}
as mentioned by rmaddy your date is UTC format so we will escape only the "T" as follow:
"2015-01-17T20:00Z".toDateFormattedWith("yyyy-MM-dd\'T\'HH:mmZ") // "Jan 17, 2015, 6:00 PM"
If you need some reference formatting your dates you can use this one;