I have a column time_stamp of type timestamp without time zone.
While executing select now()::timestamp(0) it returns a value with PST timezone. But my system timezone is IST.
I need the same in PostgreSQL output. Please anyone help me to fix it.
Related
I have trying to convert the UTC time to local time in Oracle Developer as per query below. I needed it in a particular format after conversion but after conversion to character the time comes out to be completely different. Can anyone tell me what am I doing wrong here please.
select e.encntr_id
,to_char(e.reg_dt_tm,'YYYY-MM-DD hh24:mm') as reg_dt_tm
,to_char(from_tz (cast(e.reg_dt_tm as timestamp),'UTC') at time zone
'Australia/Sydney','YYYY-MM-DD hh24:mm') as aest_reg_char
,from_tz (cast(e.reg_dt_tm as timestamp),'UTC') at time zone 'Australia/Sydney' as aest_reg
from encounter e
where e.ENCNTR_ID in(123)
encntr_id reg_dt_tm aest_reg_char aest_reg
123 2022-03-03 05:03 2022-03-03 16:03 03/MAR/22 04:51:12.000000000 PM AUSTRALIA/SYDNEY
Use TO_CHAR:
TO_CHAR(
from_tz (cast(e.reg_dt_tm as timestamp),'UTC') at time zone 'Australia/Sydney',
'YYYY-MM-DD hh24:mm:ss.ff TZR'
)
Or change the default TIMESTAMP_TZ format in SQL Developer:
ALTER SESSION SET NLS_TIMESTAMP_TZ_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF TZR';
and then run the query.
db<>fiddle here
What is the behavior of PostgreSQL when we cast a DATE to TIMESTAMP to TIMESTAMPTZ
What time zone is used?
PostgreSQL server
Client that run the query (Current session)
If you cast a date to a timestamp, time zones don't play a role, because both data types are without a time zone. The resulting timestamp will be the beginning of the day.
If you cast date to timestamp with time zone, resulting timestamp will be the beginning of the date in the time zone defined by the parameter timezone in your current session.
SHOW timezone;
TimeZone
---------------
Europe/Vienna
(1 row)
SELECT CAST (DATE '2021-01-15' AS timestamp);
timestamp
---------------------
2021-01-15 00:00:00
(1 row)
SELECT CAST (DATE '2021-01-15' AS timestamp with time zone);
timestamptz
------------------------
2021-01-15 00:00:00+01
(1 row)
Casting date to timestamp will append time 00:00:00.0 to the date.
The time zone of the current server session will be used.
By default this is the time zone setting of Postgresql server.
You can change the time zone of the current server session like this:
set time zone 'Europe/Sofia';
I do not think that the time zone of the client has any effect. More on this issue here.
Edit
As Adrian Klaver noticed "When dealing with timestamps it's best to assume the worst". Therefore better set the session time zone explicitly.
Given the situation where one needs to change the column type from integer (as epoc seconds) to timzezonetz ->
casting directly from integer to timezonetz is not possible.
but you can do this:
ALTER TABLE table_name ALTER COLUMN column_name TYPE timestamptz
USING column_name::abstime::timestamptz
I have one server which is on UTC time and one which is on EST. Now I dumped the database from the UTC one and imported it to the EST one. As timestamps are always saved as UTC I cannot find a reason the reason I get two different results for the same query:
select reported_on at time zone 'UTC', temperature from data order by reported_on desc;
UTC Server:
temperature | device | timezone
-------------+--------------------------------------+----------------------------
17.2 | ------------------------------------ | 2020-05-05 12:13:16.256+00
EST Server:
temperature | device | timezone
-------------+--------------------------------------+----------------------------
17.2 | ------------------------------------ | 2020-05-05 14:13:16.256+02
What am I missing here? How can I query the data without the timezones, I need the UTC time, not the +02 time? How can I achieve this?
Edit:
I added the lines through nodejs:
INSERT INTO data(device, reported_on, temperature, humidity) VALUES($1, to_timestamp(' + Date.now() /1000.0 + '), $2, $3) RETURNING *
The Typ of the column is:
reported_on TIMESTAMP,
Update:
Altering the timezone fixed the issue!
ALTER DATABASE sensors SET timezone TO 'UTC';
SELECT pg_reload_conf();
This is about your local database configuration. I created a dummy database locally and the result was this:
test=# CREATE TABLE timestamptest (timezone TIMESTAMPTZ);`
Showed my timezone pattern:
test=# SHOW TIMEZONE;
TimeZone
----------
UTC
(1 row)
And inserted some values inside:
test=# SELECT * FROM timestamptest;
timezone
-------------------------------
2020-05-05 15:26:27.377549+00
2020-05-05 15:28:14.014597+00
(2 rows)
Now, I changed the local timezone variable:
test=# SET TIME ZONE 'America/Montreal';
SET
And selected the info again:
test=# INSERT INTO timestamptest VALUES (now());
INSERT 0 1
test=# SELECT * FROM timestamptest ;
timezone
-------------------------------
2020-05-05 11:26:27.377549-04
2020-05-05 11:28:14.014597-04
(2 rows)
And my timezone is different because the SET command:
test=# SHOW timezone;
TimeZone
------------------
America/Montreal
(1 row)
You can change your local configuration and, about your selects showed in your question, the import seems to be correct, just the local timestamp configuration needed to be set equals from one to another.
Note that -04 on the end of the timestamp shows that your time has changed 4 hours in relation of -00 originally. Just a formatting ouptut.
More information here: here on postgresql docs
The statement "timestamps are always saved as UTC" is incorrect. Timestamp without time (timestamp) is stored with local time, timestamp with time zone (timestamptz) is always stored in UTC. From the documentation:
timestamp without time zone, PostgreSQL will silently ignore any time
zone indication. That is, the resulting value is derived from the
date/time fields in the input value, and is not adjusted for time
zone.
For timestamp with time zone, the internally stored value is always in
UTC (Universal Coordinated Time, traditionally known as Greenwich Mean
Time, GMT). An input value that has an explicit time zone specified is
converted to UTC using the appropriate offset for that time zone. If
no time zone is stated in the input string, then it is assumed to be
in the time zone indicated by the system's TimeZone parameter, and is
converted to UTC using the offset for the timezone zone.
Additional be very careful using 'EST', or any of the other timezone abbreviations, instead use the full timezone name. The abbreviations indicate a fixed UTC offset (i.e. EST is always UTC-5, and EDT is always UTC-4) and do not recognize Daylight Savings Time (DST). On the other hand the full names (i.e. are US/Central' or 'America/Montreal' or any other full timezone name) are DST aware and adjust UTC offset accordingly.
Unlike the abbreviations shown in pg_timezone_abbrevs, many of these
names imply a set of daylight-savings transition date rules.
You can observe this with:
select * from pg_timezone_abbrevs where abbrev in ('EDT', 'EST')
select * from pg_timezone_names where name in ('US/Eastern','America/New_York','America/Montreal')
The type of the column is TIMESTAMP*"
I guess there's your problem. You'll want to use TIMESTAMP WITH TIME ZONE instead. Alternatively, do not use AT TIME ZONE 'UTC' in your SELECT statement, so that you just get back the same timestamp that was stored, regardless of timezone.
What is happening in SELECT reported_on AT TIME ZONE 'UTC' is that the stored date is converted from the database's local timezone to UTC. In your second database with a different local timezone, that's a different conversion, leading to the offset in the result.
I have a PostgreSQL table with date field in the following format
2017-09-07T17:24:33+08:00
and I want to convert it to UTC time.
I've looked around but found no way to do that with this specific time format. What am I missing?
Thanks
timezone definition (https://www.postgresql.org/docs/9.1/functions-datetime.html) : The function timezone(zone, timestamp) is equivalent to the SQL-conforming construct timestamp AT TIME ZONE zone
SELECT timezone('UTC','2017-09-07T17:24:33+08:00');
if selecting from column,
with t as (
SELECT '2017-09-07T17:24:33+08:00' as tm
)
SELECT timezone('UTC',tm::timestamptz) as ts
from t;
I have a PostgreSQL table with date field in the following format: 2017-09-07T17:24:33+08:00
This is incorrect. Per Postgres documentation,
All timezone-aware dates and times are stored internally in UTC. They are converted to local time in the zone specified by the TimeZone configuration parameter before being displayed to the client.
To display a TIMESTAMP WITH TIME ZONE attribute (which, again, is stored internally in UTC) in a specific time zone, you have a few options:
By default, “They are converted to local time in the zone specified by the TimeZone configuration parameter before being displayed to the client.” This can be set in postgresql.conf, using the SQL command SET TIME ZONE, or using a number of other options.
Use the AT TIME ZONE construct.
So, in regards to your original question: You don't have to do anything to your timestamptz for Postgres to store it in UTC. To display your attribute in UTC, you can either change the TimeZone configuration paramter, or use the construct below:
SELECT dt_with_timezone AT TIME ZONE 'UTC' FROM my_table
I run a Postgres 8.3 database where times seem to be stored in UTC without time zone.
I am trying to display in local time but not with '+01' suffix :
With select scheduled_start_ts I get :
2014-01-20 05:01:35.663
With select scheduled_start_ts at time zone 'MET' :
2014-01-20 05:01:35.663+01
I would like to get "2014-01-20 06:01:35.663" which is in local time.
The database I am using cannot be modified and I am not allowed to modify how data are stored.
If you want to format times, use the to_char function. See formatting functions in the docs.
regress=> SELECT to_char(
(TIMESTAMP '2014-01-20 05:01:35.663' AT TIME ZONE 'UTC')
AT TIME ZONE 'MET',
'YYYY-MM-DD HH:MI:SS'
);
to_char
---------------------
2014-01-20 06:01:35
(1 row)
The (TIMESTAMP 'xxx' AT TIME ZONE 'UTC') gets me a timestamptz with the correct time, by re-interpreting the TIMESTAMP as being in UTC. The second AT TIME STAMP instead converts the timestamptz into a timestamp in timezone MET. This then gets formatted.
Whatever the SQL standards committe were smoking when they designed this, I never, ever, ever want to be anywhere near it.