Oracle 21c

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alter session set nls_timestamp_tz_format = 'YYYY-MM-DD HH24:MI:SS TZR'
-- get New York DST start time as UTC
with cte (ts) as (
  select timestamp '2013-03-10 01:59:59 America/New_York' from dual
  union all
  select timestamp '2013-03-10 03:00:00 America/New_York' from dual
)
select ts, to_char(ts, 'TZD') as tzd, ts at time zone 'UTC' as ts_utc
from cte


TS
TZD
TS_UTC


2013-03-10 01:59:59 AMERICA/NEW_YORK
EST
2013-03-10 06:59:59 UTC

2013-03-10 03:00:00 AMERICA/NEW_YORK
EDT
2013-03-10 07:00:00 UTC


select timestamp '2013-03-11 02:22:21 UTC' at time zone 'America/New_York' from dual;


TIMESTAMP'2013-03-1102:22:21UTC'ATTIMEZONE'AMERICA/NEW_YORK'


2013-03-10 22:22:21 AMERICA/NEW_YORK


-- get UTC timestamp as New York
with cte (ts) as (
  select timestamp '2013-03-11 02:22:21 UTC' from dual
)
select ts as ts_utc, ts at time zone 'America/New_YORK' as ts, to_char(ts at time zone 'America/New_York', 'TZD') as tzd
from cte


TS_UTC
TS
TZD


2013-03-11 02:22:21 UTC
2013-03-10 22:22:21 AMERICA/NEW_YORK
EDT

TS	TZD	TS_UTC
2013-03-10 01:59:59 AMERICA/NEW_YORK	EST	2013-03-10 06:59:59 UTC
2013-03-10 03:00:00 AMERICA/NEW_YORK	EDT	2013-03-10 07:00:00 UTC