rails日期格式

Date
====
            db:'%Y-%m-%d'   2008-08-20
  long_ordinal:'&proc'      August 20th, 2008
          long:'%B %e, %Y'  August 20, 2008
        rfc822:'%e %b %Y'   20 Aug 2008
        number:'%Y%m%d'     20080820
         short:'%e %b'      20 Aug

DateTime
========
            db:'%Y-%m-%d'   2008-08-20 16:56:21
  long_ordinal:'&proc'      August 20th, 2008 16:56
          long:'%B %e, %Y'  August 20, 2008 16:56
        rfc822:'%e %b %Y'   Wed, 20 Aug 2008 16:56:21 -0600
        number:'%Y%m%d'     20080820165621
         short:'%e %b'      20 Aug 16:56

Time
====
            db:'%Y-%m-%d %H:%M:%S'         2008-08-20 16:56:21
  long_ordinal:'&proc'                     August 20th, 2008 16:56
          long:'%B %d, %Y %H:%M'           August 20, 2008 16:56
        rfc822:'%a, %d %b %Y %H:%M:%S %z'  Wed, 20 Aug 2008 16:56:21 -0600
         short:'%d %b %H:%M'               20 Aug 16:56
        number:'%Y%m%d%H%M%S'              20080820165621
          time:'%H:%M'                     16:56