I have a PostgreSQL table named testing with a column named creation_time as timestamp with time zone. The database timezone is UTC
Now I want to get all rows whose time is greater than 00:00 of the current day as per the timezone "America/New_York".
I know how to get all rows after local midnight:
SELECT * FROM testing
WHERE ( creation_time >= now()::date)
ORDER BY id DESC
But how to use this query with a different timezone?
Assuming "the current day" is also defined by NY time, not by the current timezone setting.
SELECT *
FROM testing
WHERE creation_time >= date_trunc('day', now() AT TIME ZONE 'America/New_York') AT TIME ZONE 'America/New_York'
ORDER BY id DESC;
Yes, AT TIME ZONE 'America/New_York' twice. No typo there.
now() AT TIME ZONE 'America/New_York') gets local NY time. date_trunc gets 00:00 of that day. The 2nd AT TIME ZONE 'America/New_York' converts the local time back to timestamptz, which we finally compare to.
If you want NY 00:00 of your local date, it's simpler:
WHERE creation_time >= CURRENT_DATE::timestamp AT TIME ZONE 'America/New_York'
Same time, but can be a different day!
CURRENT_DATE is the local date (date according to the time zone setting of the current session). Effectively the same as now()::date.
Further reading:
Ignoring time zones altogether in Rails and PostgreSQL
Related
to_date('30/03/2022', 'DD/MM/YYYY')
Underlined, as hours are not specified, that means that hour is '00:00'
I would like to specify that this is for Europe/Paris time zone region.
Can you help me set-up this ?
Thanks
A DATE data type has the components: year, month, day, hour, minute and second. It ALWAYS has those components and NEVER stores anything else (such as a time zone); so it is impossible to store a time zone in a DATE data type.
A TIMESTAMP data type has the components: year, month, day, hour, minute and second and, optionally, can store fractional seconds.
A TIMESTAMP WITH TIME ZONE data type has the components: year, month, day, hour, minute, second and time zone and, optionally, can store fractional seconds information.
Therefore, if you want to store a time zone then you should use TIMESTAMP WITH TIME ZONE and not DATE.
Your code would then be:
TO_TIMESTAMP_TZ('30/03/2022 Europe/Paris', 'DD/MM/YYYY TZR')
or using a timestamp literal:
TIMESTAMP '2022-03-30 00:00:00 Europe/Paris'
or, if you want to pass in your date in that format and add the time zone in a two-step process:
FROM_TZ(TO_TIMESTAMP('30/03/2022', 'DD/MM/YYYY'), 'Europe/Paris')
db<>fiddle here
ERROR: timestamp units "timezone" not supported
That's the error I get for all timezone fields.
Here's a minimal query you can run:
select extract(timezone_hour from now()::timestamptz at time zone 'US/Eastern');
What I want is the utc offset in hours. So this should return -4.
The requirement is that I use a dynamic time zone in the query. So I have a table of "facilities" with time zone strings, and I need to get the current time for each one.
So my end query should look something like this:
SELECT
EXTRACT(timezone_hour from now() with time zone timezone) # timezone is the name of the field
FROM facilities;
I thought I had it for a second with this, but this is giving me my current offset, not the offset of the tz I'm passing:
select
extract(timezone_hour from (select now()::timestamp at time zone 'US/Eastern'))
date_part
-----------
-7
I ended up getting this to work with creating two timestamps, one at utc and one at the desired time zone, but I'll leave this open just in case there's a better solution than my current one:
select
extract(hour from (
select (
select now() at time zone 'US/Eastern') - (select now() at time zone 'UTC')));
date_part
-----------
-4
I am working with time data that is currently stores in UTC but I want it to be in PST, which is 8 hours behind. I have a pretty lengthy and involved query, but the only thing I am interested in is the time right now so I have included those parts. I want to convert the times to PST and then group by the date for the last week of data. The query has the following structure:
select
date_trunc('day', time1) AT TIME ZONE 'US/Pacific'
...
where
time1 AT TIME ZONE 'US/Pacific' > now() AT TIME ZONE current_setting('TimeZone') - INTERVAL '168 HOURS'
...
group by date_trunc('day', time1)
This results in the following time groupings. From my understanding, it groups from the 0:00 UTC, which is 16:00 in PST. However, I want the groupby to start at 0:00 PST. How do I do this? Right now, the counts in each group are misleading for each day because they go from 4 pm to 4 pm instead of 12 am to 12 am. For example, Sundays have uncharacteristically high counts because Sunday includes part of Monday's data in the groupby. I would appreciate any input to fix this issue. Thank you.
The answer depends on whether it is a timestamp with time zone or one without:
If it's a timestamp with time zone, you can convert to PST with select time1 AT TIME ZONE 'US/Pacific' and get the date with select date_trunc('day', time1 AT TIME ZONE 'US/Pacific')
If it's a timestamp without time zone stored in UTC that you want to convert, you first have to tell PostgreSQL to interpret it as UTC, then convert it, like so: select (time1 AT TIME ZONE 'Z') AT TIME ZONE 'US/Pacific' and of course you can get the date with select date_trunc('day', (time1 AT TIME ZONE 'Z') AT TIME ZONE 'US/Pacific')
In either case you have to convert time zones before truncating to the day level or you may end up with inaccurate results.
I have a column called login_timestamp, which is of type TIMESTAMP WITH TIME ZONE.
To retrieve the month for this timestamp, I would do: EXTRACT(MONTH FROM login_timestamp).
However, I would like to retrieve the month for a specific time zone (in my case, Pakistan), but can't figure out how to do that.
Documentation for this is under Date/Time Functions and Operators. Search that page for "at time zone".
select extract(month from login_timestamp at time zone 'Asia/Karachi');
You can change the time zone for a single session or for a single transaction with set session... or set local.... For example, this changes the time zone for the current session.
set session time zone 'Asia/Karachi';
Use the AT TIME ZONE construct:
SELECT EXTRACT(MONTH FROM login_timestamp AT TIME ZONE '-5');
-5 is the constant offset for Pakistan.
Details:
Ignoring timezones altogether in Rails and PostgreSQL
Try applying AT TIME ZONE. Demo
select extract(month from cast ('2017-07-01 01:00+03' as TIMESTAMP WITH TIME ZONE) AT TIME ZONE '+08') as monthNo
returns
monthno
1 6
Here I am trying to convert date column value from CET to CST.
I tried using NEW_TIME(SYSDATE ,'CET','CST') function, but it's giving an error saying unknown time zone. Issue here is CET is not recognised by oracle as valid timezone.
I tried using "at timezone" approach initially, but it's inserting the timezone name in the column value, which I don't want.
The three-character timezones don't adjust for daylight savings. To do that you need to use the fully specified timezone name. To illustrate, in Canada, there is central standard time, but the province of Saskatechewan does not use daylight savings, so if I want to convert right now to local time in summer where daylight savings is in play, and knowing the correct fully specified timezone names in the DB Timezone file (You can check the list installed in your DB by select * from V$TIMEZONE_NAMES;):
SELECT 'Central' locale
, extract(timezone_abbr from cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Canada/Central') tz_abbrv
, CAST(cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Canada/Central' as timestamp) local_time from dual
union all
SELECT 'Saskatchewan' locale
, extract(timezone_abbr from cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Canada/Saskatchewan') tz_abbrv
, CAST(cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Canada/Saskatchewan' as timestamp) local_time from dual;
LOCALE TZ_ABBRV LOCAL_TIME
Central CDT 03/08/2016 9:57:24.000000 AM
Saskatchewan CST 03/08/2016 8:57:24.000000 AM
Otherwise you would need to code when to switch between CST and DST in your calculations - bearing in mind that the rules for when daylight savings starts and ends has changed over time, and may change again in the future.
So respond to your comment about inserts, you need to first ensure that the column is defined to include the time zone (datatype "timestamp with timezone"), and change the CAST from "timestamp" to "timestamp with time zone" to make sure that the zone information is stored:
e.g.)
create table mbt (stz timestamp with time zone)
insert into mbt values (CAST(cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Indian/Maldives' as timestamp with time zone) )
insert into mbt values (CAST(cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Canada/Eastern' as timestamp with time zone) )
commit;
select * from mbt;
STZ
05/08/2016 8:06:49.000000 PM +05:00
05/08/2016 11:06:50.000000 AM -04:00
If you don't include the WITH TIME ZONE you should still get the changed value, but you won't be able to easily translate from local time to a different timezone as the values will be assumed to be in the server timezone:
drop table mbt;
create table mbt (stz timestamp);
insert into mbt values (CAST(cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Indian/Maldives' as timestamp) );
insert into mbt values (CAST(cast(add_months(sysdate,6) as timestamp) AT TIME ZONE 'Canada/Eastern' as timestamp ) );
commit;
select * from mbt;
STZ
-------------------------------
05-AUG-16 08.13.16.000000 PM
05-AUG-16 11.13.16.000000 AM
To remove timezone you can use cast(.... as Timesamp).
Check my example.
select cast( current_timestamp at time zone 'CST' as timestamp), cast( current_timestamp at time zone 'CST' as timestamp with time zone) from dual;