wb.add_worksheet(name: 'all events') do |sheet|
  bold_style = wb.styles.add_style(b: true)
  row = ['Event ID', 'Title', 'Abstract', 'Start time', 'Submitter', 'Speaker', 'Event Type', 'Track', 'Difficulty Level', 'Room', 'State']
  sheet.add_row row, style: bold_style

  @events.each do |event|
    row = []
    row << event.id
    row << event.title
    row << event.abstract
    row << (event.time.present? ? "#{event.time.strftime("%Y-%m-%d")} #{event.time.strftime("%I:%M%p")} " : '')
    row << event.submitter.name
    row << event.speaker_names
    row << event.event_type.title
    row << (event.track.present? ? event.track.name : '')
    row << (event.difficulty_level.present? ? event.difficulty_level.title : '')
    row << (event.room.present? ? event.room.name : '')
    row << event.state
    sheet.add_row row
  end
end