         return Int.max
     }
     
+    /**
+     *  The duration of the `TimePeriod` in days.
+     *  Returns the max int if beginning or end are nil.
+     */
     var days: Int {
         if self.beginning != nil && self.end != nil {
             return self.beginning!.daysEarlier(than: self.end!)

        return Int.max
    }
    
    var hours: Int {
        if self.beginning != nil && self.end != nil {
            return self.beginning!.hoursEarlier(than: self.end!)

        return Int.max
    }
    
    /**
     *  The duration of the `TimePeriod` in seconds.
     *  Returns the max int if beginning or end are nil.
     */
    var seconds: Int {
        if self.beginning != nil && self.end != nil {
            return self.beginning!.secondsEarlier(than: self.end!)
