PostgreSQL/Date Timezone/date trunc

date_trunc("hour", now())

postgres=#
postgres=# SELECT date_trunc("hour", now());
       date_trunc
------------------------
 2006-10-08 15:00:00-07
(1 row)
postgres=#
postgres=#

date_trunc("minute", now())

postgres=# SELECT date_trunc("minute", now());
       date_trunc
------------------------
 2006-10-08 15:12:00-07
(1 row)
postgres=#

date_trunc("year", now())

postgres=#
postgres=# SELECT date_trunc("year", now());
       date_trunc
------------------------
 2006-01-01 00:00:00-08
(1 row)
postgres=#