docs: improve AT TIME ZONE description
The previous description was unclear. Also add a third example, change
use of time zone acronyms to more verbose descriptions, and add a
mention that using 'time' with AT TIME ZONE uses the current time zone
rules.
Backpatch-through: 9.3
Branch
------
REL_11_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/838fd62cab520a5ae15fdab30d0f962070571bdb
Modified Files
--------------
doc/src/sgml/func.sgml | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)