# File lib/icalendar/parser.rb, line 90
    def parse_wkstart(string)
      match = string.match(/;WKSTART=(SU|MO|TU|WE|TH|FR|SA)(;|$)/)
      if match
        %w{SU MO TU WE TH FR SA}.index(match[1])
      else
        nil
      end
    end