title: Convert DateTime.Now to Seconds
body: <p>I am trying to write a function that will convert a DateTime.Now instance to the number of seconds it represents so that I can compare that to another DateTime instance.  Here is what I currently have:</p>
  
  <pre><code>public static int convertDateTimeToSeconds(DateTime dateTimeToConvert)
      {
          int secsInAMin = 60;
          int secsInAnHour = 60 * secsInAMin;
          int secsInADay = 24 * secsInAnHour;
          double secsInAYear = (int)365.25 * secsInADay;
  
          int totalSeconds = (int)(dateTimeToConvert.Year * secsInAYear) + 
                         (dateTimeToConvert.DayOfYear * secsInADay) +
                         (dateTimeToConvert.Hour * secsInAnHour) +
                         (dateTimeToConvert.Minute * secsInAMin) + 
                         dateTimeToConvert.Second;
  
          return totalSeconds;
      }
  </code></pre>
  
  <p>I realize that I am truncating the calculation for seconds in a year, but I don't need my calculation to be precise.  I'm really looking to know if the method that I am using to calculate seconds is correct.</p>
  
  <p>Does anyone have anything that could better compute seconds given from a DateTime object?  </p>
  
  <p>Also, Should the return type be int64 if I am coding in C# if I am going to calculate all the seconds since 0 AD?</p>