DateTime.Now vs DateTime.UtcNow

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Please note that this post does not take into account any other perspective of when to use DateTime.Now or DateTime.UtcNow other than performance.

This morning I tried to find numbers that compare DateTime.Now and DateTime.UtcNow but all I found was long discussions on the subject of when to use them. So I decided to write a quick sample myself to see.

Last value was 2013-03-16 12:50:18
DateTime.Now:           00:00:06.6733481 for 10000000 iterations
Last value was 2013-03-16 11:50:18
DateTime.UtcNow:        00:00:00.0741262 for 10000000 iterations
DateTime.UtcNow is 1,11% of DateTime.Now

   1:  class Program

   2:  {

   3:      static void Main(string[] args)

   4:      {

   5:          const int iterations = 10000000;

   6:          DateTime dt = DateTime.UtcNow;

   7:          Stopwatch sw = Stopwatch.StartNew();

   8:          for (int i = 0; i < iterations; i++)

   9:              dt = DateTime.Now;

  10:          sw.Stop();

  11:          Console.WriteLine("Last value was {0}", dt);

  12:          Console.WriteLine("DateTime.Now:\t\t{0} for {1} iterations", sw.Elapsed, iterations);

  13:          double nowMs = sw.ElapsedMilliseconds;

  14:          sw = Stopwatch.StartNew();

  15:          for (int i = 0; i < iterations; i++)

  16:              dt = DateTime.UtcNow;

  17:          sw.Stop();

  18:          Console.WriteLine("Last value was {0}", dt);

  19:          Console.WriteLine("DateTime.UtcNow:\t{0} for {1} iterations", sw.Elapsed, iterations);

  20:          double utcNowMs = sw.ElapsedMilliseconds;

  21:          Console.WriteLine("DateTime.UtcNow is {0:0.00}% of DateTime.Now", CalcPercentage(utcNowMs, nowMs));

  22:          Console.ReadLine();

  23:      }

  24:      private static double CalcPercentage(double value, double max)

  25:      {

  26:          double p = (100.0 / max);

  27:          return p * value;

  28:      }

  29:  }