Swift decoding error on date type based on user settings preferences (time format) [duplicate]

Recently I have noticed that an API which return a reponse that contains some date type are failing if I have a 12 hour format (AM/PM) on my phone enable iOS 17.6.1. If I switch to 24 hour format the decoding works as expected.

extension DateFormatter { /// Return example: 2022-08-24T17:25:00.000-0400 static let iso8601Full: DateFormatter = { let formatter = DateFormatter() formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ" return formatter }() }

I use it on Dependency Container as

let decoder = JSONDecoder() decoder.dateDecodingStrategy = .formatted(.iso8601Full) .. DependencyContainer.register(decoder as JSONDecoder)

The response is like:

optInDateTime = "2025-01-14T12:32:09.179Z";

While the structure is as:

struct Program: Codable, Hashable { let active: Bool let optInDateTime: Date let optOutDateTime: Date? let program: String }

The error message is:

Swift.DecodingError.dataCorrupted(Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "profile", intValue: nil), CodingKeys(stringValue: "loyaltyPrograms", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "optInDateTime", intValue: nil)], debugDescription: "Date string does not match format expected by formatter.", underlyingError: nil)) "\n"

A solution that I found can be by adding a local identified "en_US_POSIX". To modify as this

static let iso8601Full: DateFormatter = { let formatter = DateFormatter() formatter.locale = Locale(identifier: "en_US_POSIX") print("[Debugg] Locale: \(String(describing: formatter.locale))") formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ" return formatter }()

Then I have to use the same line wherever I use the DateFormatter class.

I want to know why this happens, what's the difference when I turn on 24 hour format and when 12 hour format, what affect the decoding when then response is the same.

Note: I have been able to produce on iOS 17.1.2 but not on others like 26 and 18, but some users have the issue on versions like 26, its kind of randomly.