[pg104@dbserver ~]$ psql -d postgres
psql (10.4)
Type "help" for help.
postgres=# select version();
version
---------------------------------------------------------------------------------------------------------
PostgreSQL 10.4 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-28), 64-bit
(1 row)
postgres=# select pg_postmaster_start_time();
pg_postmaster_start_time
-------------------------------
2018-05-23 15:34:15.448087-04
(1 row)
postgres=# select current_timestamp;
current_timestamp
-------------------------------
2018-05-24 01:57:24.582325-04
(1 row)
postgres=# select date_trunc('second', current_timestamp-pg_postmaster_start_time());
date_trunc
------------
10:24:04
(1 row)
postgres=# select date_trunc('minute', current_timestamp-pg_postmaster_start_time());
date_trunc
------------
10:24:00
(1 row)
postgres=# select date_trunc('hour', current_timestamp-pg_postmaster_start_time());
date_trunc
------------
10:00:00
(1 row)
postgres=# select date_trunc('day', current_timestamp-pg_postmaster_start_time());
date_trunc
------------
00:00:00
(1 row)
postgres=#
