class ActiveSupport::TimeZone

def [](arg)

Returns +nil+ if no such time zone is known to the system.
timezone to find. (The first one with that offset will be returned.)
numeric value it is either the hour offset, or the second offset, of the
is interpreted to mean the name of the timezone to locate. If it is a
Locate a specific time zone object. If the argument is a string, it 
def [](arg)
  case arg
    when String
    begin
      @lazy_zones_map[arg] ||= create(arg)
    rescue TZInfo::InvalidTimezoneIdentifier
      nil
    end
    when Numeric, ActiveSupport::Duration
      arg *= 3600 if arg.abs <= 13
      all.find { |z| z.utc_offset == arg.to_i }
    else
      raise ArgumentError, "invalid argument to TimeZone[]: #{arg.inspect}"
  end
end