This code snippet for Datetimepicker Custome Formate.

private void Form1_Load(object sender, EventArgs e)
{
dateTimePicker1.Format = DateTimePickerFormat.Custom;
dateTimePicker1.CustomFormat = "dd-MM-yyyy";
dateTimePicker2.Format = DateTimePickerFormat.Custom;
dateTimePicker2.CustomFormat = "dd-MMM-yyyy";
dateTimePicker3.Format = DateTimePickerFormat.Custom;
dateTimePicker3.CustomFormat = "dd-MMM-yy";
dateTimePicker4.Format = DateTimePickerFormat.Custom;
dateTimePicker4.CustomFormat = "MMM-dd-yyyy";
}