8.3: timestamp subtraction

Hi,

 

I don't know why this query returns false:

 

SELECT '20040506 070809.010000'::timestamp(6) - '20010203 040506.007000'::timestamp(6) = '1188 day 3 hour 3 minute 3 second 3 millisecond'::interval;

If I just subtract the two timestamps, its result is the interval I specified.

 

What may cause this?

 

Thanks,

Otto