Took me a while to figure out how to get at all the time zone abbreviations stored within the TZInfo gem. I'm sure there's a better way, but this works.

time_zones_by_abbreviation.rb

abbrevs = {}
TZInfo::Timezone.all.each do |tz|
  tz = tz.send(:real_timezone) unless tz.class == TZInfo::Timezone
  tzi = tz.send(:info)
  offsets = tzi.instance_variable_get(:@offsets)
  next if offsets.blank?
  offsets.values.each do |offset|
    abbrevs[offset.abbreviation] ||= []
    abbrevs[offset.abbreviation] << tz.identifier
  end
end