lookup function returning 00-jan-00 date values.

In my current workbook I have a lookup function that looks up dates in other Excel files:

=IFERROR(VLOOKUP(A2,Lookup2013NonCephs,9,0),IFERROR(VLOOKUP(A2,Lookup2013Cephs,9,0),IFERROR(VLOOKUP(A2,Lookup2012NonCephs,9,0),IFERROR(VLOOKUP(A2,Lookup2012Cephs,9,0),IFERROR(VLOOKUP(A2,Lookup2011NonCephs,9,0),IFERROR(VLOOKUP(A2,Lookup2011Cephs,9,0),IFERROR(VLOOKUP(A2,Lookup2010NonCephs,9,0),IFERROR(VLOOKUP(A2,Lookup2010Cephs,9,0),""))))))))

However, the function is returning a date value of 00-Jan-00 whenever no date is found against the lookup value in A2.

The cell should be left blank if that's the case and not display 00-Jan-00.

Can anyone recommend how that can be achieved?