title: DateTime represent how many bit in C#
body: <p>Int, Float, Double, Decimal, DateTime .etc are value types. And I know:</p>
  
  <pre><code>Int:Represents a 32-bit signed integer.
  Float:Represents a single-precision floating-point number(32-bit).
  Double:Represents a double-precision floating-point number(64-bit).
  ...
  </code></pre>
  
  <p>But how many bit for DateTime? And why all value types in .NET are struct?</p>