title: undefined method `change' DateTime in IRB console
body: <p>change(:hour => 1) working fine in rails console </p>
  
  <pre><code>irb(main):004:0&gt; dt = DateTime.now
  =&gt; Mon, 10 Dec 2012 15:52:01 -0800
  irb(main):005:0&gt; _.change(:hour =&gt; 1)
  =&gt; Mon, 10 Dec 2012 01:00:00 -0800
  irb(main):006:0&gt;
  irb(main):007:0&gt; dt.class
  =&gt; DateTime
  irb(main):008:0&gt;
  </code></pre>
  
  <p>But throws “undefined method `change'” in irb</p>
  
  <pre><code>irb(main):008:0&gt; require 'active_record'
  =&gt; true
  irb(main):009:0&gt; dt = DateTime.now
  =&gt; #&lt;DateTime: 2012-12-10T15:55:14-08:00 (10611097185737/4320000,-1/3,2299161)&gt;
  irb(main):010:0&gt; dt.class
  =&gt; DateTime
  irb(main):011:0&gt; dt.change(:hour =&gt; 1)
  NoMethodError: undefined method `change' for #&lt;DateTime:0x53e20a9a&gt;
          from (irb):11:in `evaluate'
          from org/jruby/RubyKernel.java:1070:in `eval'
          from org/jruby/RubyKernel.java:1395:in `loop'
          from org/jruby/RubyKernel.java:1178:in `catch'
          from org/jruby/RubyKernel.java:1178:in `catch'
          from C:\PF\jruby-1.7.0.preview2\bin\irb:13:in `(root)'
  irb(main):012:0&gt;
  </code></pre>
  
  <p>Any suggestion how to make it work?</p>
  
  <p>Thanks in advance.</p>