title: Date::today not defined?
body: <p>Why are only some methods of the Date class loaded without an explicit:</p>
  
  <pre><code>require 'date'
  </code></pre>
  
  <p>line?</p>
  
  <p>For example:</p>
  
  <pre><code>irb(main):002:0&gt; Date.today
  NoMethodError: undefined method `today' for Date:Class
  from (irb):2
  from /Users/mwlang/.rvm/rubies/ruby-2.0.0-p0/bin/irb:16:in `&lt;main&gt;'
  </code></pre>
  
  <p>And then...</p>
  
  <pre><code>irb(main):003:0&gt; require 'date'
  =&gt; true
  </code></pre>
  
  <p>leads to...</p>
  
  <pre><code>irb(main):004:0&gt; Date.today
  =&gt; #&lt;Date: 2013-04-12 ((2456395j,0s,0n),+0s,2299161j)&gt;
  </code></pre>
  
  <p>The documentation at <a href="http://ruby-doc.org/stdlib-2.0/libdoc/date/rdoc/Date.html">http://ruby-doc.org/stdlib-2.0/libdoc/date/rdoc/Date.html</a> seems to offer no explicit explanation for this behavior.  Comments on #irc say its a stdlib rather than core library, but core doesn't even have Date class defined and launching irc with -f (suppress reading .irbrc) to get a minimal load still appears to load some sort of base/core Date class.</p>
  
  <p>Would like a technical explanation of what's going on and references to the Ruby docs that explain this so I understand for other such encounters as I switch from Ruby 1.8.7 to Ruby 2.0.0.</p>