There is no such thing as "Persian DateTime." The value is DateTimealways the Gregorian value of the calendar without special formatting. When you format it (usually by calling ToString), you can determine how it is formatted, and if you use a culture that uses a non-Gregorian calendar, it will convert the original value to this calendar.
, , , , :
DateTime date = DateTime.Parse(text, persianCulture);
string englishText = date.ToString(englishCulture);