title: Why is there no DateTime.AddWeeks(), and how can I get a DateTime object for 52 weeks ago?
body: <p>The <code>System.DateTime</code> object has methods to <code>AddYears(), AddMonths(), AddDays(), AddSeconds()</code>, etc.</p>
  
  <p>I've noticed that there is no <code>AddWeeks()</code>. Why is this?</p>
  
  <p>Also, my requirement is to get a price value from 52 weeks ago. I know this equates to 1 year, but they were specific about 52 weeks. </p>
  
  <p>Would it be the same for me to do:</p>
  
  <pre><code>yearOldPrice = _priceService.GetPriceForDate(price.Date.AddYears(-1));
  </code></pre>
  
  <p>as</p>
  
  <pre><code>yearOldPrice = _priceService.GetPriceForDate(price.Date.AddDays(-7 * 52));
  </code></pre>
  
  <p>I ask on the presumption that <code>.AddDays(-7 * 52)</code> is the same as <code>.AddWeeks(-52)</code>, 'cause there's 7 days in a week.</p>