Not.

You don't store such a value. It is valid only today, and you can do
this calculation in a query or in a report if you need it.

The age calculation is spelled in Access as

DateDiff("yyyy", birthday, Date())

Don't.

If you store people's ages in a table, half of them on average will be
WRONG six months from now; every single one will be WRONG a year from
now.

Instead, store just the birthdate; in a Query or as the control source
of a Form or Report textbox you can calculate the age (as of the
moment you run the query) using the expression

Age: DateDiff("yyyy", [DOB], Date()) - IIF(Format([DOB], "mmdd") >
Format(Date(), "mmdd"), 1, 0)

The IIF() corrects the age by subtracting a year if the person's
birthday has not yet arrived.

                 John W. Vinson[MVP]    
   Come for live chats every Tuesday and Thursday
http://go.compuserve.com/msdevapps?loc=us&access=public

Like everyone says, you don't even try to set it up as a column in a table.
If you want to calcuate it in a query or on a form, though, this might
help:

'
' Provide a helpfully formatted output of calculated age
'
Public Function IntelligentAge(BirthDate As Date) As String
 Dim strAge As String
 Dim dwAgeInDays As Long
 Dim dblDateInUnits As Double
 Dim dblBirthDateInUnits As Double
 
 ' Days is the only thing we can really bank on
 dwAgeInDays = Date - DateValue(BirthDate)

 ' Okay, let's do some stratification
 Select Case dwAgeInDays
 Case Is < 15 ' up to two weeks

   strAge = dwAgeInDays & " days"
   
 Case 15 To 182 ' two weeks to six months

   strAge = Int(dwAgeInDays / 7) & " weeks"
   
 Case 183 To 730 ' six months to two years

   dblDateInUnits = 12 * Year(Date) + Month(Date) + _
     (Day(Date) / Day(DateSerial(Year(Date), Month(Date) + 1, 0)))

   dblBirthDateInUnits = 12 * Year(BirthDate) + _
        Month(BirthDate) + _
       (Day(BirthDate) / Day(DateSerial(Year(BirthDate), _
                                      Month(BirthDate) + 1, _
                                      0)))
       
   strAge = Format$(dblDateInUnits - dblBirthDateInUnits, _
                    "0.0 ""months""")
       
 Case Is > 730 ' over two years
   ' decimal ages are used in medicine a lot: but you
   ' can simplify this if you want whole numbers of years
   '
   ' calculate a decimal date for today
   dblDateInUnits = Year(Date) + _
       (CDbl(Format$(Date, "y")) / _
       CDbl(Format$(DateSerial(Year(Date) + 1, 1, 0), "y")))
   
   ' calculate a decimal date for the birthdate
   dblBirthDateInUnits = Year(BirthDate) + _
       (CDbl(Format$(BirthDate, "y")) / _
       CDbl(Format$(DateSerial(Year(BirthDate) + 1, 1, 0), "y")))

   ' subtract them for a decimal age        
   strAge = Format$(dblDateInUnits - dblBirthDateInUnits, "0.0 ""years""")
   
 End Select

 ' return the formatted value  
 IntelligentAge = strAge
 
End Function

Hope that helps

Tim F