Conversion timestamp to simple phrase interval

NSDate+.swift

extension NSDate {
    class func relativeTimeInString(value: NSTimeInterval) -> String {
        func getTimeData(value: NSTimeInterval) -> (count: Int, suffix: String) {
            let count = Int(floor(value))
            let suffix = count != 1 ? "s" : ""
            return (count: count, suffix: suffix)
        }

        let value = -value
        switch value {
            case 0...15: return "just now"

            case 0..<60:
                let timeData = getTimeData(value)
                return "\(timeData.count) second\(timeData.suffix) ago"

            case 0..<3600:
                let timeData = getTimeData(value/60)
                return "\(timeData.count) minute\(timeData.suffix) ago"

            case 0..<86400:
                let timeData = getTimeData(value/3600)
                return "\(timeData.count) hour\(timeData.suffix) ago"

            case 0..<604800:
                let timeData = getTimeData(value/86400)
                return "\(timeData.count) day\(timeData.suffix) ago"

            default:
                let timeData = getTimeData(value/604800)
                return "\(timeData.count) week\(timeData.suffix) ago"
        }
    }
}

Usage:

let time = NSDate(timeIntervalSince1970: timestamp).timeIntervalSinceNow
let relativeTimeString = NSDate.relativeTimeInString(time)
print(relativeTimeString)