Date Calculation in Form Fields

[Guest]

I want to calculate a date using form fields somethingn like this:

Date1 + 4 days = NewDate

to allow me to put expiry dates on a document (it could be 4 days or 4
years!)

I can get calculation to return an answer using:

{=Date1 + 4 /@"d-MMM-yy"}

but the answer doesn't make sense... ...with Date1 = 24 Aug 04 the
answer is being returned as 32?

Does anyone know how I can tackle this? The document is too complex
to transfer into excel or even use an excel table where I want the
field to report the answer.

Thanks

Calum