class RubyXL::Workbook

def initialize(worksheets=[], filepath=nil, creator=nil, modifier=nil, created_at=nil,
               company='', application=APPLICATION,
               appversion=APPVERSION, date1904=0)
  if worksheets.nil? || worksheets.empty?
    @worksheets       = [Worksheet.new(self,SHEET_NAME)]
  else
    @worksheets       = worksheets
  end
  @filepath           = filepath
  @creator            = creator
  @modifier           = modifier
  @company            = company
  @application        = application
  @appversion         = appversion
  @num_fmts           = nil
  @fonts              = nil
  @fills              = nil
  @borders            = nil
  @cell_xfs           = nil
  @cell_style_xfs     = nil
  @cell_styles        = nil
  @shared_strings     = nil
  @calc_chain         = nil #unnecessary?
  @num_strings        = 0 #num strings total
  @size               = 0 #num strings in shared_strings array
  @date1904           = date1904 > 0
  @external_links     = nil
  @style_corrector    = nil
  @drawings           = nil
  @worksheet_rels     = nil
  @printer_settings   = nil
  @macros             = nil
  @colors             = nil
  @shared_strings_XML = nil
  @defined_names      = nil
  begin
    @created_at       = DateTime.parse(created_at).strftime('%Y-%m-%dT%TZ')
  rescue
    t = Time.now
    @created_at       = t.strftime('%Y-%m-%dT%TZ')
  end
  @modified_at        = @created_at
  fill_styles()
  fill_shared_strings()
end