tag:graysoftinc.com,2014-03-20:/tags/Leap%20Year 2014-04-10T20:27:59Z James Edward Gray II tag:graysoftinc.com,2008-02-29:/posts/46 2014-04-10T20:27:59Z

A small reminder that dates can be tricky.

<p>I had to debug some tests that just started failing first thing this morning. I guess I should have procrastinated though, because they would have magically fixed themselves tomorrow morning. The cause of the one day only bug: Leap Year Day, of course.</p> <p>If you run the following code on a day like today, February 29th 2008, <code>Date</code> will choke on your invalid date:</p> <div class="highlight highlight-ruby"><pre><span class="nb">require</span> <span class="s2">"date"</span> <span class="k">class</span> <span class="nc">Date</span> <span class="c1"># Returns a Date in the past +year_offset+ years ago.</span> <span class="k">def</span> <span class="nc">self</span><span class="o">.</span><span class="nf">years_ago</span><span class="p">(</span><span class="n">year_offset</span><span class="p">)</span> <span class="n">now</span> <span class="o">=</span> <span class="n">today</span> <span class="no">Date</span><span class="o">.</span><span class="n">civil</span><span class="p">(</span><span class="n">now</span><span class="o">.</span><span class="n">year</span> <span class="o">-</span> <span class="n">year_offset</span><span class="p">,</span> <span class="n">now</span><span class="o">.</span><span class="n">month</span><span class="p">,</span> <span class="n">now</span><span class="o">.</span><span class="n">day</span><span class="p">)</span> <span class="k">end</span> <span class="k">end</span> <span class="nb">puts</span> <span class="no">Date</span><span class="o">.</span><span class="n">years_ago</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> </pre></div> <p>I came up with the following fix, which is accurate enough for my purposes:</p> <div class="highlight highlight-ruby"><pre><span class="nb">require</span> <span class="s2">"date"</span> <span class="k">class</span> <span class="nc">Date</span> <span class="c1"># Returns a Date in the past +year_offset+ years ago.</span> <span class="k">def</span> <span class="nc">self</span><span class="o">.</span><span class="nf">years_ago</span><span class="p">(</span><span class="n">year_offset</span><span class="p">)</span> <span class="n">today</span> <span class="o">-</span> <span class="mi">365</span> <span class="o">*</span> <span class="n">year_offset</span> <span class="k">end</span> <span class="k">end</span> <span class="nb">puts</span> <span class="no">Date</span><span class="o">.</span><span class="n">years_ago</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> </pre></div> <p>I'm not 100% sure that covers all cases though, so use with caution. Date's are tricky business!</p> James Edward Gray II