Convert timestamp string with epochal time and timezone into NSDate

Question

I have a String in following format

"/Date(573465600000-0800)/"

How do I convert this to regular NSDate object?

Answer 1

The first part "573465600000" is the time since the Unix epoch in milliseconds, and the second part "-0800" is a time zone specification.

Here is a slight modification of Parsing JSON (date) to Swift which also covers the time zone part:

extension NSDate {
    convenience init?(jsonDate: String) {
        let prefix = "/Date("
        let suffix = ")/"
        let scanner = NSScanner(string: jsonDate)

        // Check prefix:
        if scanner.scanString(prefix, intoString: nil) {

            // Read milliseconds part:
            var milliseconds : Int64 = 0
            if scanner.scanLongLong(&milliseconds) {
                // Milliseconds to seconds:
                var timeStamp = NSTimeInterval(milliseconds)/1000.0

                // Read optional timezone part:
                var timeZoneOffset : Int = 0
                if scanner.scanInteger(&timeZoneOffset) {
                    let hours = timeZoneOffset / 100
                    let minutes = timeZoneOffset % 100
                    // Adjust timestamp according to timezone:
                    timeStamp += NSTimeInterval(3600 * hours + 60 * minutes)
                }

                // Check suffix:
                if scanner.scanString(suffix, intoString: nil) {
                    // Success! Create NSDate and return.
                    self.init(timeIntervalSince1970: timeStamp)
                    return
                }
            }
        }

        // Wrong format, return nil. (The compiler requires us to
        // do an initialization first.)
        self.init(timeIntervalSince1970: 0)
        return nil
    }
}

Example:

if let theDate = NSDate(jsonDate: "/Date(573465600000-0800)/") {
    println(theDate)
} else {
    println("wrong format")
}

Output:

1988-03-04 00:00:00 +0000

---

Update for Swift 3 (Xcode 8):

extension Date {
    init?(jsonDate: String) {
        let prefix = "/Date("
        let suffix = ")/"
        let scanner = Scanner(string: jsonDate)

        // Check prefix:
        guard scanner.scanString(prefix, into: nil)  else { return nil }

        // Read milliseconds part:
        var milliseconds : Int64 = 0
        guard scanner.scanInt64(&milliseconds) else { return nil }
        // Milliseconds to seconds:
        var timeStamp = TimeInterval(milliseconds)/1000.0

        // Read optional timezone part:
        var timeZoneOffset : Int = 0
        if scanner.scanInt(&timeZoneOffset) {
            let hours = timeZoneOffset / 100
            let minutes = timeZoneOffset % 100
            // Adjust timestamp according to timezone:
            timeStamp += TimeInterval(3600 * hours + 60 * minutes)
        }

        // Check suffix:
        guard scanner.scanString(suffix, into: nil) else { return nil }

        // Success! Create NSDate and return.
        self.init(timeIntervalSince1970: timeStamp)
    }
}

Example:

if let theDate = Date(jsonDate: "/Date(573465600000-0800)/") {
    print(theDate)
} else {
    print("wrong format")
}