System.Globalization.DateTimeFormatInfo g = new System.Globalization.DateTimeFormatInfo();
dateTimePicker1.Value = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1);
dateTimePicker2.Value = new DateTime(DateTime.Now.Year, DateTime.Now.Month, g.Calendar.GetDaysInMonth(DateTime.Now.Year, DateTime.Now.Month));