Calculated field feature might be useful

See Delphi Help on calculated field. With calculated field feature in
Delphi, you do not need to have age field in your actual table, just the
date of birth field (DOB).
Introduce a new field in Fields Editor (right-click on the TTable/TQuery
component and select "Fields Editor..."). Right click on Field Editor dialog
to choose "New field" option.
Give this new field name AGE with field type of  Integer. In the Field Type
group, choose Calculated from the radio boxes. Click OK to close.

You will see AGE in the Fields Editor. Open Object Inspector for this field.
Set ReadOnly property to False since the user do not need to edit this field
for sure! You can set DefaultExpression to 0. Close this dialog. Set
AutoCalcFields property in TTable/TQuery to True.

Select OnCalcFields event handler of the TTable/TQuery where you have
introduced the new AGE field.
Use DOB field to calculate current age: AGE.value := AgeAtDate(DOB.Value,
Now); That all, folks!

function AgeAtDate (const DOB, DT: TDateTime): Integer;
var
   D1, M1, Y1, D2, M2, Y2: Word;
begin
   if DT < DOB then
      Result := -1
   else
   begin
      DecodeDate (DOB, Y1, M1, D1);
      DecodeDate (DT, Y2, M2, D2);
      Result := Y2 - Y1;
      if (M2 < M1) or ((M2 = M1) and (D2 < D1)) then
         Dec (Result);
   end;
End;

From: "Giovanni ILARI" <ilari...@tin.it>
Subject: how calculate the age of a person??
Date: 16 Oktober 2000 15:21

hello, i am a beginner on delphi 4, i should like to calculate, on derivated
field on paradox 7 database of delphi, age of a person with currently date:
today date - date of birthday, so how can i write this program?
thank's for give me instructions, John