The following bug has been logged online:
Bug reference:      5966
Logged by:          Ricardo Solanilla
Email address:      info(at)abaco-tandil(dot)com(dot)ar
PostgreSQL version: 8.3.0  b.1400
Operating system:   windows nt
Description:        extract(epoch..) function error
Details: 
-- try this
select (extract(epoch from (date('2011-03-20'))) - extract(epoch from
(date('2011-03-19')))) / 3600
-- it must be 24 (hours), only occurs in march 19,2011
-- in v. 8.0 work fine!!