00:00:00 DateTime toString become 12:00:00

00:00:00 DateTime toString become 12:00:00


I have a datetime '2013-8-5 0:00:00'.
When I parse it to string using .ToString("yyyy-MM-dd hh:mm:ss"), it
returns "2013-08-05 12:00:00"
Did I write it wrong?
new SqlParameter("@StartDate", SqlDbType.DateTime)
{
Value = startDate.ToString("yyyy-MM-dd hh:mm:ss")
}