The time part is discarded.

[hellower]

pg: 15
oracle:12c

SELECT * FROM
dblink.query('server_oracle','select owner, object_name, object_id, created from dba_objects where rownum < 10')
as t(c1 text, c2 text, c3 integer, c4 timestamp);

---

SYS .xdk_version_12.2.0.1.0_production 58117 2019-03-28 00:00:00 <========= 00:00:00 !! truncated!
SYS ACCESS$ 84 2019-03-28 00:00:00
SYS ACLMV$ 606 2019-03-28 00:00:00
SYS ACLMV$_BASE_VIEW 8182 2019-03-28 00:00:00
SYS ACLMV$_MVINFO 8181 2019-03-28 00:00:00
SYS ACLMV$_REFLOG 612 2019-03-28 00:00:00
SYS ACLMVREFSTAT$ 610 2019-03-28 00:00:00
SYS ACLMVSUBTBL$ 608 2019-03-28 00:00:00
SYS ADD_NUMBER_DEFINER 591051 2019-04-09 00:00:00