I need a function that calculates and returns a person's age in years based on his/her birthdate and current date. For example, a person born 5/30/68 would be 21 years old on 5/27/90. Here's what I have so far:

var month, day, year: integer;
var curmonth, curday, curyr: integer;

function Age (month, day, year: integer
curmonth, curday, curyr: integer): integer;
var agemonth: integer;
var ageday: integer;
var ageyr: integer;
var age: integer;

begin {main}
write ('Enter birth month, day, and year numerically ');
readln (birmth, birday, birdyr);
age := Age (month, day, year, curmonth, curday, curyr);
writeln ('Your age is ', age)

This is taken from the SWAG archive and I think it is what you need.

{
Allright... I checked around a lot of DATE and TIME routines, and came up
with this, taken from about three different routines. This routine works,
as far as I know, and I've implemented it successfully into my own code.
If anyone knows that this routine has a bug in it, please let me know.

This procedure uses the Julian calander mathmatical equasions to convert
two dates and give the # of days inbetween. If anyone knows a faster way
of writing this procedure, please let me know.
}

type
string80=string[80];

var
_retval:integer;

procedure check_date(stream1,stream2:string80);
var
internal1,internal2:longint;
JNUM:real;
cd,month,day,year: integer;
out:string[25];

function Jul( mo, da, yr: integer): real;
var
i, j, k, j2, ju: real;
begin
i := yr; j := mo; k := da;
j2 := int( (j - 14)/12 );
ju := k - 32075 + int(1461 * ( i + 4800 + j2 ) / 4 );
ju := ju + int( 367 * (j - 2 - j2 * 12) / 12);
ju := ju - int(3 * int( (i + 4900 + j2) / 100) / 4);
Jul := ju;
end;

begin
out:=copy(stream1,1,2);
if copy(out,1,1)='0' then delete(out,1,1);
val(out,month,cd);
out:=copy(stream1,4,2);
if copy(out,1,1)='0' then delete(out,1,1);
val(out,day,cd);
out:=copy(stream1,7,2);
if copy(out,1,1)='0' then delete(out,1,1);
val(out,year,cd);
jnum:=jul(month,day,year);
str(jnum:10:0,out);
val(out,internal1,cd);
out:=copy(stream2,1,2);
if copy(out,1,1)='0' then delete(out,1,1);
val(out,month,cd);
out:=copy(stream2,4,2);
if copy(out,1,1)='0' then delete(out,1,1);
val(out,day,cd);
out:=copy(stream2,7,2);
if copy(out,1,1)='0' then delete(out,1,1);
val(out,year,cd);
jnum:=jul(month,day,year);
str(jnum:10:0,out);
val(out,internal2,cd);
_retval:=internal1-internal2;
end;

begin
check_date('01-01-95','01-01-94');
writeln('The # of days inbetween is = ',_retval);
end.

you should be able to do something like in the rest of your function:

if ( ageday < 0) then
agemonth := agemonth-1;

if (agemonth<0) then
ageyr :=ageyr-1;

if (ageyr < 0 ) then
/* bad date */
ageyr:=0;

age := ageyr;

/* of course this assumes the dates entered are valid dates*/

0

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procedure date_difference(y1, m1, d1, y2, m2, d2 : integer);
var
yeardiff, monthdiff, daydiff, plus : integer;
diffok : boolean;
begin
yeardiff := 0;
monthdiff := 0;
daydiff := 0;
plus := 0;
diffok := true;
if d1 >= d2 then
daydiff := d1 - d2
else
begin
daydiff := 31 - (d2 - d1);
plus := 1;
end;
m2 := m2 + plus;
plus := 0;
if m1 >= m2 then
monthdiff := m1 - m2
else
begin
monthdiff := 12 - (m2 - m1);
plus := 1;
end;
y2 := y2 + plus;
if y1 >= y2 then
yeardiff := y1 - y2
else
diffok := false;
if diffok then
begin
write('The difference in dates is ', yeardiff, ' year(s) ', monthdiff);
writeln(' month(s) ', daydiff, ' day(s)');
end
else
writeln('Error. The second date was more modern - bigger - than the first date');
end;

begin
writeln('This program expects first date inputted to be newer - bigger - than 2nd');
writeln('On next 3 lines enter year, month, day of first date');
readln(year1);
readln(month1);
readln(day1);
writeln('On next 3 lines enter year, month, day of second date');
readln(year2);
readln(month2);
readln(day2);
date_difference(year1, month1, day1, year2, month2, day2);
end.

0

RoelPotmanCommented:

Another suggestion/addition:

Success !

Age = (sysdate - birthdate) / 10000

Sysdate = date of today lay-out ccyymmdd for example 20001121 (Nov. 21, 2000)
Birthdate = lay-out ccyyymmdd for example 19921228 (Dec. 28, 1992)