If you want to change the culture of your entire application, you can set the culture when the application starts as follows:
Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US", false);
MSDN.
, . ToShortDateString() en-US, . ToString() , , :
aDateTime.ToString("MM/dd/yyyy");
System.Globalization :
System.Globalization.CultureInfo culture = new System.Globalization.CultureInfo("en-US");
string datePattern = culture.DateTimeFormat.ShortDatePattern;
string shortDate = aDateTime.ToString(datePattern);