TimeDate格式化输出：
DateTime.parse(Time.now.to_s).strftime(\'%Y-%m-%d %H:%M:%S\').to_s #就是按照2013-8-16 16：42：13的格式输出
如果只想输出日期，而不要输出具体时间
DateTime.parse(Time.now.to_s).strftime(\'%Y-%m-%d\').to_s #就是按照2013-8-16格式输出
反向格式化（将字符串转化为日期格式）：
DateTime.parse(params[\'date\']).strftime(\'%Y-%m-%d %H:%M:%S\').to_s
接下来介绍rails自带的TimeDate格式
如果你忘记了rails自带的TimeDate格式，那么在命令行输入：
> rake date_formats
执行命令后，可以看到如下
1 Date 2 ==== 3 db:\'%Y-%m-%d\' 2009-12-04 4 short:\'%e %b\' 4 Dec 5 number:\'%Y%m%d\' 20091204 6 long:\'%B %e, %Y\' December 4, 2009 7 long_ordinal:\'&proc\' December 4th, 2009 8 rfc822:\'%e %b %Y\' 4 Dec 2009 9 10 DateTime 11 ======== 12 db:\'%Y-%m-%d\' 2009-12-04 15:38:38 13 short:\'%e %b\' 04 Dec 15:38 14 number:\'%Y%m%d\' 20091204153838 15 long:\'%B %e, %Y\' December 04, 2009 15:38 16 long_ordinal:\'&proc\' December 4th, 2009 15:38 17 rfc822:\'%e %b %Y\' Fri, 04 Dec 2009 15:38:38 +0800 18 19 Time 20 ==== 21 short:\'%d %b %H:%M\' 04 Dec 15:38 22 db:\'%Y-%m-%d %H:%M:%S\' 2009-12-04 15:38:38 23 number:\'%Y%m%d%H%M%S\' 20091204153838 24 long:\'%B %d, %Y %H:%M\' December 04, 2009 15:38 25 long_ordinal:\'&proc\' December 4th, 2009 15:38 26 rfc822:\'%a, %d %b %Y %H:%M:%S %z\' Fri, 04 Dec 2009 15:38:38 中国标准时间 27 time:\'%H:%M\' 15:38
简单的格式化例子： Time.now.to_s(:db) #格式为2013-8-16
接下来介绍，集成多种方式输出
1 # config/initializers/date_time_formats.rb 2 Time::DATE_FORMATS.merge!( 3 :full => \'%B %d, %Y at %I:%M %p\', 4 :md => \'%m/%d\', 5 :mdy => \'%m/%d/%y\', 6 :time => \'%I:%M %p\' 7 )
简单的格式化例子：Time.now.to_s(:full) #格式为"August 16, 2013 at 17:32 PM"
要是要求是当前年份，不显示年，其他的年才显示
1 Time::DATE_FORMATS.merge!( 2 :friendly => lambda { |time| 3 if time.year == Time.now.year 4 time.strftime "%b #{time.day.ordinalize}" 5 else 6 time.strftime "%b #{time.day.ordinalize}, %Y" 7 end 8 } 9 )
>> Time.now.to_s(:friendly) => "August 16th" >> (Time.now-2.years).to_s(:friendly) => "August 16th, 2011"
