row["DO_Date"].ToString()
returns a string which depends on your local system regional datetime setting.
Try doing the following:
DateTime dt = DateTime.ParseExact(row["DO_Date"].ToString("yyyy-MM-dd HH:mm:ss"), "yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture);
In other words - force the source format to be the same as the one you are trying to convert to.
There is a simpler way though:
DateTime dt = (DateTime)row["DO_Date"]
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