Doubts in timespan

Hello all,

I'm having some problems with timespan type.

I have in the same table an attribute named "inserted_time" with
datetime type and another attribute named "elapsed_time" with timespan
type.

When I'll insert a new entry in this table, I need to calculate the
difference between last "inserted_time" and new "inserted_time", and
update "elapsed_time" in the last row.

I used the following command:

"UPDATE tasktime SET elapsed_time='age((SELECT inserted_time FROM
tasktime WHERE row=$row),(SELECT inserted_time FROM tasktime WHERE
row=$old_row))' WHERE row=$old_row"

And I received the message:

"PostgresSQL query failed: ERROR: Bad timespan external representation
'age(Thu Aug 26 09:31:00 1999 EST, Thu Aug 26 09:29:00 1999 EST)'"

I tried to change the update command as follow:

"UPDATE tasktime SET elapsed_time='age($actual_inserted_time,
$old_inserted_time)' WHERE row=$old_row"

And I received the same message.

Any body knows where are my mistake ????

Any body could explain how is the data in a timespan type ????

Thanks in advance,

Paulo Roberto Kappke
Cyclades Corporation