rails의 날짜 시간 형식

task :date_formats => :environment do
  now = Time.now
  [:to_date, :to_datetime, :to_time].each do |conv_meth|
    obj = now.send(conv_meth)
    puts obj.class.name
    puts "=" * obj.class.name.length
    name_and_fmts = obj.class::DATE_FORMATS.map { |k, v| [k, %Q('#{String === v ? v : '&proc'}')] }
    max_name_size = name_and_fmts.map { |k, _| k.to_s.length }.max + 2
    max_fmt_size = name_and_fmts.map { |_, v| v.length }.max + 1
    name_and_fmts.each do |format_name, format_str|
      puts sprintf("%#{max_name_size}s:%-#{max_fmt_size}s %s", format_name, format_str, obj.to_s(format_name))
    end
    puts
  end
end

Date
====
db:'%Y-%m-%d'         2009-12-04
short:'%e %b'         4 Dec
number:'%Y%m%d'       20091204
long:'%B %e, %Y'      December 4, 2009
long_ordinal:'&proc'  December 4th, 2009
rfc822:'%e %b %Y'     4 Dec 2009

DateTime
========
db:'%Y-%m-%d'         2009-12-04 15:38:38
short:'%e %b'         04 Dec 15:38
number:'%Y%m%d'       20091204153838
long:'%B %e, %Y'      December 04, 2009 15:38
long_ordinal:'&proc'  December 4th, 2009 15:38
rfc822:'%e %b %Y'     Fri, 04 Dec 2009 15:38:38 +0800
       
Time
====
short:'%d %b %H:%M'            04 Dec 15:38
db:'%Y-%m-%d %H:%M:%S'         2009-12-04 15:38:38
number:'%Y%m%d%H%M%S'          20091204153838
long:'%B %d, %Y %H:%M'         December 04, 2009 15:38
long_ordinal:'&proc'           December 4th, 2009 15:38
rfc822:'%a, %d %b %Y %H:%M:%S %z'  Fri, 04 Dec 2009 15:38:38       
time:'%H:%M'                   15:38