To set date format globally in global.asax

using System.Globalization;
using System.Threading;

//...
protected void Application_BeginRequest(Object sender, EventArgs e)
{    
  CultureInfo newCulture = (CultureInfo)  

System.Threading.Thread.CurrentThread. 

CurrentCulture.Clone();

 
  newCulture.DateTimeFormat.ShortDatePattern = "dd-MMM-yyyy";
  newCulture.DateTimeFormat.DateSeparator = "-";
  Thread.CurrentThread.CurrentCulture = newCulture;
}