Solution 1
To avoid that behaviour, please define the collection of columns:
SELECT StringField1, IntField2, FORMAT(DateField3, 'MM/dd/yyyy') AS Field3
FROM [Sheet1$]
or
SELECT StringField1, IntField2, CDate(DateField3) AS Field3
FROM [Sheet1$]
Above code should works too ;)
For further information, please see:
How To Use ADO.NET to Retrieve and Modify Records in an Excel Workbook With Visual Basic .NET[
^]
Microsoft Jet Database Engine Programmer's Guide - Introduction [
^]
Solution 2
Before you start importing data, please, format cells as a date.
More:
How to control and understand settings in the Format Cells dialog box in Excel[
^]