     /// Creates a new instance with given `value` in specified
     /// `unit`. `baseValue` is calculaed based on `value` and `unit`.
     ///
-    /// - Parameter value: Number of units.
-    /// - Parameter unit: Unit in which `Timestamp` is represented.
+    /// - Parameters:
+    ///     - value: Number of units.
+    ///     - unit:  Unit in which `Timestamp` is represented.
     init(value: Int, unit: Unit) {
         self.init(value: Double(value), unit: unit)
     }

    let value: Double

    /// Represnts a unit in which `Timestamp` calculates `baseValue`.
    let unit: Unit

    /// Represents a value which doesn't depend on any unit
    /// or unit's value. It can be treated as a base unit
    /// which all `Unit`s can be calculated from or stored in.
    /// Its value depends on a multiplier specified for each `Unit`.
    let baseValue: Double

    /// Creates a new instance with given `value` in specified
    /// `unit`. `baseValue` is calculaed based on `value` and `unit`.
    ///
    /// - Parameter value: Number of units.
    /// - Parameter unit: Unit in which `Timestamp` is represented.
    init(value: Double, unit: Unit) {
        self.value = value
        self.unit = unit

    }
}

// MARK: - Arithmetic Operators

/// Returns new `Timestamp` which is a result of adding `baseValues`
/// of both parameters. New `Timestamp` has the same `Unit` as `lhs`.
