big int

This isn't exactly related to pg but
I thought some wise person might be able
to explain.

i've been storing the number of seconds
since  Dec 31 19:00:00 1969 whenever
I have to store a time format. For this
integer type is good.

As we all know come year 2032 or so this
number will exceed the range of integer.

If I want to prevent problems in the future
should I use int8.  Is there significant
overhead?  It seems that on an DEC/alpha
64 bit platform perl does not seems
to be aware that it's not on a 32 bit platform.
--------------
% perl -MTime::Local -e 'print timelocal(9,9,9,9,9,200)' ;
Can't handle date (9, 9, 9, 9, 9, 200) at -e line 1
--------------

Thanks