在我的情况下，我必须将DynamoDB - lastUpdated列(Unix时间戳)转换为正常时间。

lastUpdated的初始值是:1460650607601 -转换为2016-04-14 16:16:47 +0000通过:

   if let lastUpdated : String = userObject.lastUpdated {

                let epocTime = NSTimeInterval(lastUpdated)! / 1000 // convert it from milliseconds dividing it by 1000

                let unixTimestamp = NSDate(timeIntervalSince1970: epocTime) //convert unix timestamp to Date
                let dateFormatter = NSDateFormatter()
                dateFormatter.timeZone = NSTimeZone()
                dateFormatter.locale = NSLocale.currentLocale() // NSLocale(localeIdentifier: "en_US_POSIX")
                dateFormatter.dateFormat =  "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
                dateFormatter.dateFromString(String(unixTimestamp))

                let updatedTimeStamp = unixTimestamp
                print(updatedTimeStamp)

            }

斯威夫特5

如果你的目标系统是iOS 11.0+ / macOS 10.13+，你只需使用带有withInternetDateTime和withFractionalSeconds选项的ISO8601DateFormatter，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"

基于对象范例中可接受的答案

class ISO8601Format
{
    let format: ISO8601DateFormatter

    init() {
        let format = ISO8601DateFormatter()
        format.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
        format.timeZone = TimeZone(secondsFromGMT: 0)!
        self.format = format
    }

    func date(from string: String) -> Date {
        guard let date = format.date(from: string) else { fatalError() }
        return date
    }

    func string(from date: Date) -> String { return format.string(from: date) }
}


class ISO8601Time
{
    let date: Date
    let format = ISO8601Format() //FIXME: Duplication

    required init(date: Date) { self.date = date }

    convenience init(string: String) {
        let format = ISO8601Format() //FIXME: Duplication
        let date = format.date(from: string)
        self.init(date: date)
    }

    func concise() -> String { return format.string(from: date) }

    func description() -> String { return date.description(with: .current) }
}

callsite

let now = Date()
let time1 = ISO8601Time(date: now)
print("time1.concise(): \(time1.concise())")
print("time1: \(time1.description())")


let time2 = ISO8601Time(string: "2020-03-24T23:16:17.661Z")
print("time2.concise(): \(time2.concise())")
print("time2: \(time2.description())")

iOS10或更新版本使用ISO8601DateFormatter。

在iOS9或更早版本使用DateFormatter。

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
        }
    }()
}

在未来的格式可能需要改变，这可能是一个小头痛有日期。dateFromISO8601调用应用程序中的所有地方。使用类和协议来包装实现，在一个地方更改日期时间格式调用将更简单。如果可能的话使用RFC3339，它是一个更完整的表示。DateFormatProtocol和DateFormat非常适合依赖注入。

class AppDelegate: UIResponder, UIApplicationDelegate {

    internal static let rfc3339DateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
    internal static let localeEnUsPosix = "en_US_POSIX"
}

import Foundation

protocol DateFormatProtocol {

    func format(date: NSDate) -> String
    func parse(date: String) -> NSDate?

}


import Foundation

class DateFormat:  DateFormatProtocol {

    func format(date: NSDate) -> String {
        return date.rfc3339
    }

    func parse(date: String) -> NSDate? {
        return date.rfc3339
    }

}


extension NSDate {

    struct Formatter {
        static let rfc3339: NSDateFormatter = {
            let formatter = NSDateFormatter()
            formatter.calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierISO8601)
            formatter.locale = NSLocale(localeIdentifier: AppDelegate.localeEnUsPosix)
            formatter.timeZone = NSTimeZone(forSecondsFromGMT: 0)
            formatter.dateFormat = rfc3339DateFormat
            return formatter
        }()
    }

    var rfc3339: String { return Formatter.rfc3339.stringFromDate(self) }
}

extension String {
    var rfc3339: NSDate? {
        return NSDate.Formatter.rfc3339.dateFromString(self)
    }
}



class DependencyService: DependencyServiceProtocol {

    private var dateFormat: DateFormatProtocol?

    func setDateFormat(dateFormat: DateFormatProtocol) {
        self.dateFormat = dateFormat
    }

    func getDateFormat() -> DateFormatProtocol {
        if let dateFormatObject = dateFormat {

            return dateFormatObject
        } else {
            let dateFormatObject = DateFormat()
            dateFormat = dateFormatObject

            return dateFormatObject
        }
    }

}

请记住按照Technical Q&A1480中的描述将区域设置为en_US_POSIX。在Swift 3中:

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

问题是，如果您在使用非公历的设备上，年份将不符合RFC3339/ISO8601，除非您指定区域设置以及timeZone和dateFormat字符串。

或者你可以使用ISO8601DateFormatter来让你自己摆脱设置locale和timeZone的麻烦:

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，请参见此答案的先前修订。