# File lib/tzinfo/timezone.rb, line 409
    def local_to_utc(local, dst = nil)
      TimeOrDateTime.wrap(local) {|wrapped|
        if block_given?
          period = period_for_local(wrapped, dst) {|periods| yield periods }
        else
          period = period_for_local(wrapped, dst)
        end
        
        period.to_utc(wrapped)
      }
    end