class ReeDatetime::FindTimeZonesByOffset

def call(offset)
  return CACHE[offset] if CACHE.has_key?(offset)
  zones = TZInfo::Timezone
    .all_identifiers
    .select { |zone| 
       zone_offset = offset_to_string(find_tzinfo(zone).utc_offset)
       zone_offset == offset 
    }
  CACHE[offset] = zones
  zones
end