A simple ISO string parsing and converting library for Swift

ISOString.swift

public struct ISOString {
    /// Parse ISO 6709 string.
    /// e.g. "+34.0595-118.4460+091.541/"
    /// SeeAlso: [ISO 6709](https://en.wikipedia.org/wiki/ISO_6709)
    public static func parse(iso6709 text: String?) -> CLLocation? {
        guard
            let results = text?.capture(pattern: "([+-][0-9.]+)([+-][0-9.]+)"),
            let latitude = results[safe: 1] as NSString?,
            let longitude = results[safe: 2] as NSString?
            else { return nil }
        return CLLocation(latitude: latitude.doubleValue, longitude: longitude.doubleValue)
    }

    /// Convert `CLLocation` to ISO 6709 string.
    /// e.g. "+34.0595-118.4460+091.541/"
    /// SeeAlso: [ISO 6709](https://en.wikipedia.org/wiki/ISO_6709)
    public static func iso6709(from location: CLLocation) -> String {
        String(
            format: "%+09.5f%+010.5f%+.0fCRSWGS_84/",
            location.coordinate.latitude,
            location.coordinate.longitude,
            location.altitude
        )
    }

    /// Parse ISO 8601 string.
    /// e.g. "2019-07-19T13:40:59+0900"
    /// SeeAlso: [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601)
    public static func parse(iso8601 text: String?) -> Date? {
        guard
            let text = text,
            let date = ISO8601DateFormatter().date(from: text)
            else { return nil }
        return Date(timeInterval: 0, since: date)
    }

    /// Convert `Date` to ISO 8601 string.
    /// e.g. "2019-07-19T13:40:59+0900"
    /// SeeAlso: [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601)
    public static func iso8601(from date: Date) -> String {
        let formatter = ISO8601DateFormatter()
        formatter.timeZone = TimeZone.current
        formatter.formatOptions.remove(.withColonSeparatorInTimeZone) // iOS camera output format
        return formatter.string(from: date)
    }
}

private extension String {
    func capture(pattern: String) -> [String] {
        guard
            let regex = try? NSRegularExpression(pattern: pattern),
            let result = regex.firstMatch(in: self, range: NSRange(location: 0, length: count))
            else { return [] }
        return (0..<result.numberOfRanges).map { String(self[Range(result.range(at: $0), in: self)!]) }
    }
}

private extension Collection {
    subscript(safe index: Index) -> Element? {
        return indices.contains(index) ? self[index] : nil
    }
}

public extension CLLocation {
    convenience init?(iso6709 text: String?) {
        guard let location = ISOString.parse(iso6709: text) else { return nil }
        self.init(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude)
    }

    var iso6709: String {
        ISOString.iso6709(from: self)
    }
}

public extension Date {
    init?(iso8601 text: String?) {
        guard let date = ISOString.parse(iso8601: text) else { return nil }
        self = date
    }

    var iso8601: String {
        ISOString.iso8601(from: self)
    }
}

Usage

// Parse ISO 6709 string
let locationItem = AVMetadataItem.metadataItems(from: asset.metadata, filteredByIdentifier: .quickTimeMetadataLocationISO6709).first
let location = ISOString.parse(iso6709: locationItem?.stringValue)
print(String(describing: location)) // CLLocation

// Convert Date to ISO 8601 string
let now = Date()
let iso8601 = ISOString.iso8601(from: now)
let creationDateItem = AVMutableMetadataItem(identifier: .quickTimeMetadataCreationDate, value: iso8601)
print(String(describing: creationDateItem))