title: DateTime.ToString(format) unexpected behavior on different pc
body: <p>there.
  I'm developing a simple interface to get data from SQLServer and i use the function <code>DateTime.ToString(String)</code> </p>
  
  <p>The actual code is <code>DP.Value.ToString("yyyy-MM-dd HH:mm:00")</code>,
  where  DP is a DateTimePicker control.</p>
  
  <p>All works fine while I test it on my own laptop. But when I move the compiled code on another pc, the result is different.
  E.g.: It passes from <code>2013-03-27 22:02</code> to <code>2013-03-27 22.02</code>, replacing the '.' with ':' in the hour.
  But this is sufficient to crash my app, because SQLServer generate an invalid date.</p>
  
  <p>What may be the culprit?
  Both pc have SQLServer 2008 R2 (and same collation) and .NET Framework 4.0 Client Profile installed.
  A difference I have seen is that my SQLServer have the English(United States) language property, while the other have Italian setted, but I should have overcome it with the format string...</p>