Modules & VBA :: Excel File When Formatted In Access Shows Wrong Number

I am opening an excel file from access and changing the formatting from "dd/mm/yyyy hh:mm" to number with 15 decimal places.Then I am linking the file to the database and subsequently doing a lookup on the date time on the access form against this table.The excel file when formatted from vba in access shows the wrong number

datetime = 03/05/2013 11:26
database number = 41397.4763888889
Excel file number = 41398.4763888889 (which would equal 04/05/13 11:26)

now if I do it manually then I get 41397.4763888889 or if the macro is in excel I still get 41397.4763888889.Also I have tested the code with manually editing the excel file and this works fine.

Code:
Private Sub Command288_Click()
Dim s As String
Dim t As Integer
Dim ws As Worksheet
s = LaunchCD(Me)
MsgBox (s)

[code]....

also this brings up a form and then I select the field required for the lookup and with the button is pressed the rest of the code runs as follows.

Code:
Private Sub LoadData_Click()
Dim w As String
w = Forms![frmList1]![Combo0]
w = "[" & w & "]"
Dim dtA As String

[code]....