如何创建日期时间戳并格式化为ISO 8601,RFC 3339,UTC时区？

Question

如何使用ISO 8601和RFC 3339的格式标准生成日期时间戳？

目标是一个如下所示的字符串:

"2015-01-01T00:00:00.000Z"

格式:

• 年,月,日,如"XXXX-XX-XX"
• 字母"T"作为分隔符
• 小时,分钟,秒,毫秒,如"XX:XX:XX.XXX".
• 字母"Z"作为零偏移的区域指示符,也就是UTC,GMT,Zulu时间.

最佳案例:

• Swift源代码简单,简洁,直观.
• 无需使用任何其他框架,子项目,cocoapod,C代码等.

我搜索过StackOverflow,Google,Apple等,并没有找到Swift的答案.

似乎最有前途的类NSDate,NSDateFormatter,NSTimeZone.

相关问答:如何在iOS中获得ISO 8601日期？

这是迄今为止我提出的最好的:

var now = NSDate()
var formatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
formatter.timeZone = NSTimeZone(forSecondsFromGMT: 0)
println(formatter.stringFromDate(now))

Answer 1

Xcode 9•Swift 4•iOS 11或更高版本

extension ISO8601DateFormatter {
    convenience init(_ formatOptions: Options, timeZone: TimeZone = TimeZone(secondsFromGMT: 0)!) {
        self.init()
        self.formatOptions = formatOptions
        self.timeZone = timeZone
    }
}

extension Formatter {
    static let iso8601 = ISO8601DateFormatter([.withInternetDateTime, .withFractionalSeconds])
}

extension Date {
    var iso8601: String {
        return Formatter.iso8601.string(from: self)
    }
}

extension String {
    var iso8601: Date? {
        return Formatter.iso8601.date(from: self)
    }
}

用法:

Date().description(with: .current)  //  Tuesday, February 5, 2019 at 10:35:01 PM Brasilia Summer Time"
let dateString = Date().iso8601   //  "2019-02-06T00:35:01.746Z"

if let date = dateString.iso8601 {
    date.description(with: .current) // "Tuesday, February 5, 2019 at 10:35:01 PM Brasilia Summer Time"
    print(date.iso8601)           //  "2019-02-06T00:35:01.746Z\n"
}

iOS 9•Swift 3或更高版本

extension Formatter {
    static let iso8601: DateFormatter = {
        let formatter = DateFormatter()
        formatter.calendar = Calendar(identifier: .iso8601)
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.timeZone = TimeZone(secondsFromGMT: 0)
        formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
        return formatter
    }()
}

可编程协议

如果在使用Codable协议时需要对此格式进行编码和解码,则可以创建自己的自定义日期编码/解码策略:

extension JSONDecoder.DateDecodingStrategy {
    static let iso8601withFractionalSeconds = custom {
        let container = try $0.singleValueContainer()
        let string = try container.decode(String.self)
        guard let date = Formatter.iso8601.date(from: string) else {
            throw DecodingError.dataCorruptedError(in: container,
                  debugDescription: "Invalid date: " + string)
        }
        return date
    }
}

和编码策略

extension JSONEncoder.DateEncodingStrategy {
    static let iso8601withFractionalSeconds = custom {
        var container = $1.singleValueContainer()
        try container.encode(Formatter.iso8601.string(from: $0))
    }
}

游乐场测试

let dates = [Date()]   // ["Feb 8, 2019 at 9:48 PM"]

编码

let encoder = JSONEncoder()
encoder.dateEncodingStrategy = .iso8601withFractionalSeconds
let data = try! encoder.encode(dates)
print(String(data: data, encoding: .utf8)!)

解码

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601withFractionalSeconds
let decodedDates = try! decoder.decode([Date].self, from: data)  // ["Feb 8, 2019 at 9:48 PM"]

Answer 2

请记住将技术语言设置en_US_POSIX为技术问答1480中所述.在Swift 3中:

let date = Date()
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ"
formatter.timeZone = TimeZone(secondsFromGMT: 0)
formatter.locale = Locale(identifier: "en_US_POSIX")
print(formatter.string(from: date))

问题是,如果你是其中使用非公历的设备上,今年不会,除非你指定符合RFC3339/ISO8601 locale还有timeZone和dateFormat字符串.

或者你可以ISO8601DateFormatter用来让你摆脱设置locale和timeZone自己的杂草:

let date = Date()
let formatter = ISO8601DateFormatter()
formatter.formatOptions.insert(.withFractionalSeconds)  // this is only available effective iOS 11 and macOS 10.13
print(formatter.string(from: date))

对于Swift 2的演绎,请参阅此答案的上一版本.

Answer 3

如果你想使用ISO8601DateFormatter()带有Rails 4+ JSON提要的日期(当然不需要毫秒),你需要在格式化程序上设置一些选项才能正常工作,否则该date(from: string)函数将返回nil.这是我正在使用的:

extension Date {
    init(dateString:String) {
        self = Date.iso8601Formatter.date(from: dateString)!
    }

    static let iso8601Formatter: ISO8601DateFormatter = {
        let formatter = ISO8601DateFormatter()
        formatter.formatOptions = [.withFullDate,
                                          .withTime,
                                          .withDashSeparatorInDate,
                                          .withColonSeparatorInTime]
        return formatter
    }()
}

以下是使用操场截图中不包含选项的结果:

Answer 4

斯威夫特 5

如果你的目标的iOS 11.0+ / MacOS的10.13+，您只需使用ISO8601DateFormatter与withInternetDateTime和withFractionalSeconds选项，如下所示：

let date = Date()

let iso8601DateFormatter = ISO8601DateFormatter()
iso8601DateFormatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
let string = iso8601DateFormatter.string(from: date)

// string looks like "2020-03-04T21:39:02.112Z"

Answer 5

为了进一步赞美 Andrés Torres Marroquín 和 Leo Dabus，我有一个保留小数秒的版本。我在任何地方都找不到它的记录，但 Apple 将输入和输出的小数秒截断为微秒（3 位精度）（即使使用 SSSSSSS 指定，与Unicode tr35-31相反）。

我应该强调，这对于大多数用例来说可能不是必需的。在线日期通常不需要毫秒精度，当需要时，最好使用不同的数据格式。但有时必须以特定方式与预先存在的系统进行互操作。

Xcode 8/9 和 Swift 3.0-3.2

extension Date {
    struct Formatter {
        static let iso8601: DateFormatter = {
            let formatter = DateFormatter()
            formatter.calendar = Calendar(identifier: .iso8601)
            formatter.locale = Locale(identifier: "en_US_POSIX")
            formatter.timeZone = TimeZone(identifier: "UTC")
            formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSSSSXXXXX"
            return formatter
        }()
    }

    var iso8601: String {
        // create base Date format 
         var formatted = DateFormatter.iso8601.string(from: self)

        // Apple returns millisecond precision. find the range of the decimal portion
         if let fractionStart = formatted.range(of: "."),
             let fractionEnd = formatted.index(fractionStart.lowerBound, offsetBy: 7, limitedBy: formatted.endIndex) {
             let fractionRange = fractionStart.lowerBound..<fractionEnd
            // replace the decimal range with our own 6 digit fraction output
             let microseconds = self.timeIntervalSince1970 - floor(self.timeIntervalSince1970)
             var microsecondsStr = String(format: "%.06f", microseconds)
             microsecondsStr.remove(at: microsecondsStr.startIndex)
             formatted.replaceSubrange(fractionRange, with: microsecondsStr)
        }
         return formatted
    }
}

extension String {
    var dateFromISO8601: Date? {
        guard let parsedDate = Date.Formatter.iso8601.date(from: self) else {
            return nil
        }

        var preliminaryDate = Date(timeIntervalSinceReferenceDate: floor(parsedDate.timeIntervalSinceReferenceDate))

        if let fractionStart = self.range(of: "."),
            let fractionEnd = self.index(fractionStart.lowerBound, offsetBy: 7, limitedBy: self.endIndex) {
            let fractionRange = fractionStart.lowerBound..<fractionEnd
            let fractionStr = self.substring(with: fractionRange)

            if var fraction = Double(fractionStr) {
                fraction = Double(floor(1000000*fraction)/1000000)
                preliminaryDate.addTimeInterval(fraction)
            }
        }
        return preliminaryDate
    }
}

Answer 6

用途ISO8601DateFormatter上iOS10或更高版本。

用途DateFormatter上iOS9或以上。

斯威夫特 4

protocol DateFormatterProtocol {
    func string(from date: Date) -> String
    func date(from string: String) -> Date?
}

extension DateFormatter: DateFormatterProtocol {}

@available(iOS 10.0, *)
extension ISO8601DateFormatter: DateFormatterProtocol {}

struct DateFormatterShared {
    static let iso8601: DateFormatterProtocol = {
        if #available(iOS 10, *) {
            return ISO8601DateFormatter()
        } else {
            // iOS 9
            let formatter = DateFormatter()
            formatter.calendar = Calendar(identifier: .iso8601)
            formatter.locale = Locale(identifier: "en_US_POSIX")
            formatter.timeZone = TimeZone(secondsFromGMT: 0)
            formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
            return formatter
        }
    }()
}