I have next two queries to calculate a day and a half of day
tucha=> select extract( epoch from '2019-03-31'::timestamptz +interval '1day' - '2019-03-31'::timestamptz );
date_part
-----------
82800
(1 row)
tucha=> select extract( epoch from '2019-03-31'::timestamptz +interval '0.5day' - '2019-03-31'::timestamptz );
date_part
-----------
43200
(1 row)
if one day is 82800, then a half a day should be 41400, is not?
tucha=> select extract( epoch from '2019-04-01'::timestamptz -'2019-03-31'::timestamptz )/2;
?column?
----------
41400
(1 row)
NOTICE postgresql actually calculate 43200, but I expect 41400 as it calculated for last expression
NOTICE both: 1day and 0.5day periods contain time when DST occur
UPD
Is there a spec about how half a day is calculated for days when DST occur?