Fix Time::Span multiply and divide

src/time/span.cr

@@ -291,15 +291,21 @@ struct Time::Span
   end
 
   # Returns a `Time::Span` that is *number* times longer.
-  def *(number : Number) : Time::Span
+  def *(number : Int) : Time::Span
     # TODO check overflow
     Span.new(
-      seconds: to_i.to_i64 * number,
+      seconds: to_i * number,
       nanoseconds: nanoseconds.to_i64 * number,
     )
   end
 
-  def /(number : Number) : Time::Span
+  # Returns a `Time::Span` that is *number* times longer.
+  def *(number : Float) : Time::Span
+    (total_nanoseconds * number).nanoseconds
+  end
+
+  # Return a `Time::Span` that is divided by *number*.
+  def /(number : Int) : Time::Span
     seconds = to_i.tdiv(number)
     nanoseconds = self.nanoseconds.tdiv(number)
 
@@ -313,6 +319,11 @@ struct Time::Span
     )
   end
 
+  # Returns a `Time::Span` that is divided by *number*.
+  def /(number : Float) : Time::Span
+    (total_nanoseconds / number).nanoseconds
+  end
+
   def /(other : self) : Float64
     total_nanoseconds.to_f64 / other.total_nanoseconds.to_f64
   end