Our application uses CURRENT_TIMESTAMP to store an event when a user submitted the data. This is stored in a TIMESTAMP WITH LOCAL TIME ZONE type column. Our servers are in PST timezone, but I want to see what time one of our users in Australia submitted the data in Australian time? I am confused how to do this properly? When I query the database right now this column seems to show the date the row was submitted but in PST time for every row.
Something like this:
SELECT
datetime_submitted -- I want this to display the time this value was created in Australian time not PST
FROM my_table
WHERE user = 'AUSTRALIAN';
Use the AT TIME ZONE clause:
select systimestamp as server_timestamp,
systimestamp at time zone 'Australia/Sydney' as australia_timestamp
from dual;
SERVER_TIMESTAMP AUSTRALIA_TIMESTAMP
-------------------------------------- --------------------------------------
12-AUG-16 04.12.23.789000000 PM -05:00 13-AUG-16 07.12.23.789000000 AM AUSTRALIA/SYDNEY
Right now it is 4:12:23 PM on 12 August 2016 at my location (Central time, US); it is already tomorrow in Australia, as you can see from the example. (Reminds me the joke - don't worry about the end of the world coming today, it's already tomorrow in Australia!)
If you want to just look at the time in the user's time zone you can set the session to whatever time zone the user is located in then when you select the times it should give it back to you in that time zone as if you were that user.
% setenv ORA_SDTZ '+09:30'
or
ALTER SESSION SET TIME_ZONE='+9:30';
Reference for more details: https://docs.oracle.com/cd/E11882_01/server.112/e10729/ch4datetime.htm#NLSPG263
Updated
If you only want one column displayed in a different time zone then you can convert it.
To convert the timezone just in the query you can just use CAST(date_field AS TIMESTAMP) AT TIME ZONE 'US/Eastern' AS time_name on the column you want to change.
Reference for more details: https://docs.oracle.com/cd/B19306_01/server.102/b14225/ch4datetime.htm#i1007699
First, your application need to receive exact date time with user local timezone. For example, if you have typical web application with frontend, backend and database, then your frontend need to send exact date time with local user timezone (for example "2016-08-08 03:00:00CST") to your backend. Backend need to save this in a table as-is keeping date, time, timezone information received from frontend. Oracle needs to store date, time and timezone into database as-is so datetime_submitted column should have information about time zone. Suitable data type for it will be TIMESTAMP WITH TIME ZONE, as described here: https://docs.oracle.com/cd/B28359_01/server.111/b28318/datatype.htm#CDEGDFFE
Maybe you did not fully understand data type TIMESTAMP WITH LOCAL TIME ZONE. Data type TIMESTAMP WITH LOCAL TIME ZONE shows time values always and only in current user session time zone.
When you work with time zones then often you get an advise like: "Store all times in UTC time and convert displayed value at application layer." That is exactly how TIMESTAMP WITH LOCAL TIME ZONE works. The mayor difference is, times are not stored at UTC but at DBTIMEZONE (unless you set DBTIMEZONE = UTC, of course). Hence you cannot modify DBTIMEZONE setting once you have any data in a TIMESTAMP WITH LOCAL TIME ZONE column.
You get an error if you try for example TO_CHAR(datetime_submitted, 'hh24:mi:ss TZR'), because time zone region is by definition always your current user session time zone.
The database does not know the time zone of your users in Australia, because all stored times where converted to PST time zone (well, most likely to -08:00 but skip the details here).
If you like to see the values in a different time zone then you have to change your current user session time zone. Typically you do this by ALTER SESSION SET TIME_ZONE=... or by environment variable, resp. Registry setting ORA_SDTZ.
Another solution is to cast to TIMESTAMP WITH TIME ZONE or TIMESTAMP data type.
Related
Is there any convention to add in a local timezone (whatever the user has set it as) in a database?
For example, like I can do the following for UTC time:
2014-01-01 01:02:03Z
Is there something like the following to mean local time?
2014-01-01 01:02:03L
Or some other suffix where it can either pick up the user's system time or take it from a variable that can be set? For example, something like (for Postgres):
ALTER DATABASE postgres SET timezone TO 'Europe/Berlin';
This has nothing to do with Postgres.
The format you're asking about is ISO 8601. Specifically in that format, the absence of a Z or an offset such as -07:00 or +05:30 is defined as "local time".
So what you are looking for is a string without an offset, such as 2014-01-01T01:02:03.
postgres would use the system timezone, or what you called local, if no timezone is specified. see manual
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.
...
Conversions between timestamp without time zone and timestamp with time zone normally assume that the timestamp without time zone value should be taken or given as timezone local time.
Your concept is flawed for a couple of reasons:
A user in Germany connects to a Web server in England that connects to a database server is America. What constitutes local?
More to the point Postgres does not store the time zone in with time zone fields. So you will not recover the entered time zone on data retrieval.
If you are dealing with multiple time zones then the field you need to use is timestamp with time zone. This will rotate entered timestamp values to UTC for storage. You now have a fixed point in time that you can rotate to whatever 'local' time you want on retrieval.
Just treat the undecorated time as a timestamp with time zone:
richard=> SET timezone='Europe/London';
SET
richard=> SELECT '2022-08-27 21:42:22.25891'::timestamptz;
timestamptz
------------------------------
2022-08-27 21:42:22.25891+01
(1 row)
richard=> SET timezone='Europe/Paris';
SET
richard=> SELECT '2022-08-27 21:42:22.25891'::timestamptz;
timestamptz
------------------------------
2022-08-27 21:42:22.25891+02
(1 row)
I have a table storing a time value say "11:00 AM". This is what the client's would want the progress to run every day. The client also has a timezone info table letting me know which time zone its office is located. So "11:00 AM" in Eastern time zone is very different from "11:00 AM" in Pacific.
Then I have a program that checks whether the current time is what the client's desired runtime. This process runs in Eastern time zone always.
I am trying to figure out an easy way to compare whether my current time is actually the client's desired run time. What I am doing now is something like this:
Get the current DateTimeOffset of my environment. This will produce something like '2021-03-15 16:02:22.3112948 -04:00'
Then get the client's run time, which is "11:00 AM" or whatever the value, as well as client's timezone offset by using the sys.time_zone_info table. This give me the actual offset value, taking DST into consideration so that I don't have to calculate whether today is in DST or not.
I then construct a Datetimeoffset value from string by using current date value + client's run time value + the offset value. Then convert this into Eastern time zone using at time zone 'Eastern Standard Time'
By now, I have two values both in Eastern time zone and I can compare them. First question -- do you see any potential issue with my logic? Secondly, is there a better/easier way to do this?
Thanks!
This question already has answers here:
How to handle Day Light Saving in Oracle database
(4 answers)
Closed 2 years ago.
I need a bit of help in changing the time zone in the Oracle cloud infrastructure database. by default it is in UTC I want to change to +5:30 ist
Whether you use the Console or the API, the time zone options you can select from are represented in the named region format, for example, America/Los_Angeles. The Console allows you to select UTC, the time zone detected in your browser (if your browser supports time zone detection), or an alternate time zone.
To specify an alternate time zone (the Select another time zone option), you first select a value in the Region or country field to narrow the list of time zones to select from in the Time zone field. In the America/Los_Angeles example, America is the time region and Los_Angeles is the time zone. The options you see in these two fields roughly correlate with the time zones supported in both the Java.util.TimeZone class and on the Linux operating system. If you do not see the time zone you are looking for, try selecting "Miscellaneous" in the Region and country field.
see here:https://docs.oracle.com/en-us/iaas/Content/Database/References/timezones.htm
SELECT * FROM table_a
WHERE time_1 >= to_timestamp('11/01/2014 10:00 PDT', 'MM/DD/YYYY HH24:MI TZ')
time_1 is in UTC time zone and it is a timestamp with timezone. So, will this give me what I want or I need to do exact UTC time in the function to_timestamp()?
Postgresql has two different timestamp data types and it is confusing which one should be used when. The two types are:
timestamp (also known as timestamp without time zone) It is most likely that this is the type in table_a
timestamp with time zone This is the data type returned by to_timestamp()
You must be sure that you are comparing apples with apples or pairs with pairs and not mix them or you may get undesirable results.
If your table_a.time_1 is a timestamp with time zone then the code you give in your question will work fine.
If your table_a.time_1 is a timestamp then you will need to change your code:
SELECT *
FROM table_a
WHERE time_1 >= to_timestamp('11/01/2014 10:00 PDT', 'MM/DD/YYYY HH24:MI TZ') at time zone 'utc';
The last part of this (at time zone 'utc') will strip the timezone (PDT) off the specified timestamp and translate the timestamp to UTC.
Edit: to help with your comments in this answer...
In order to understand how to translate time zones you need to understand the difference between the two forms of time stamp. It will become clear why you need to understand this below. As I indicate above the difference between the two forms of time stamp is confusing. There is a good manual page but for now just read on.
The main thing to understand is that neither version actually stores a time zone (despite the name). The naming would make much more sense if you added an extra word "translation". Think "timestamp without time zone translation" and "timestamp with time zone translation".
A timestamp with time zone translation doesn't store a time zone at all. It is designed to store time stamps which could come from anywhere in the world and not loose track of their meaning. So when entering one you must provide the time zone it came from or postgresql will assume it came from the time zone of your current session. Postgresql automatically translates it out of the given time zone into an internal time zone for the server. You don't need to know what time zone that is because postgresql will always translate it back from this internal time zone before giving you the value. When you retrieve the value (eg: SELECT my_time FROM foo) postgresql translates the time stamp to the time zone of your current session. Alternatively you can specify the time zone to translate into (eg: SELECT my_time AT TIME ZONE 'PDT' FROM foo).
With that in mind it's easier to understand that a timestamp without time zone translation will never be changed from the time you specify. Postgresql will regard 11:00:00 as happening before 12:00:00 even if you meant 11 in America and 12 in England. It's easy to see why that may not be what you want.
A very common programming error is to think that a timestamp with time zone is at a particular time zone. It isn't. It is at whatever time zone you ask for it to be. And if you don't specify what time zone you want it at then postgresql will assume you want it at your current session time zone.
You've stated that your field is a timestamp with time zone which are all at UTC. This isn't technically correct. Most likely your session time zone is UTC and postgresql is giving you everything in UTC as a result.
So you have a timestamp with time zone and you want to know what these times are in PDT? Easy: SELECT my_time AT TIME ZONE 'PDT' FROM foo.
It's important to understand that the AT TIME ZONE '...' syntax toggles between timestamp and timestamp with time zone.
timestamp AT TIME ZONE 'PDT' converts into a timestamp with time zone and tells postgresql to convert to the PDT time zone.
timestamp with time zone AT TIME ZONE 'PDT' converts into a timestamp telling postgresql to interpret it as coming from 'PDT'.
This symetry means that to reverse AT TIME ZONE 'foo' you just use AT TIME ZONE 'foo'. Put another way SELECT anything AT TIME ZONE 'PDT' AT TIME ZONE 'PDT' will always leave anything unchanged.
I have a TIMESTAMP field in an hsqldb table that I want to set to "2015-02-11 16:02:01.488 America/Los_Angeles", but the insert fails even if I set the column to TIMESTAMP WITH TIMEZONE, the reason being hsqldb seems to support '2008-08-08 20:08:08-8:00' format but not spelled out like America/Los_Angeles. Is there way to make the insert accept America/Los_Angeles type zones ?
Sorry, but hsqldb doesn't support working with IANA/Olson time zones directly. You are correct that TIMESTAMP WITH TIMEZONE only supports a time zone offset. You can review the hsqldb docs for confirmation.
Many databases do not support named time zone. Oracle and Postgres support them, but most others do not.
Consider also that while a named time zone can usually determine the offset, there are still cases of ambiguity around the fall-back daylight saving time transition. In other words, if you had "2015-11-01 01:30:00 America/Los_Angeles", you could not deterministically tell whether it was Pacific Daylight Time (UTC-07:00) or Pacific Standard Time (UTC-08:00). This is why usually just the offset is stored.
The converse is also true though. If you only store "-08:00" then you can't deterministically know that it came from "America/Los_Angeles".
Here's a general guideline that will help:
If the local time is unimportant, then just store a TIMESTAMP based on UTC.
If the local time is important, but the value will never be modified, then store a TIMESTAMP WITH TIMEZONE, using the local time and it's associated time zone offset.
If the local time is important AND the value can be modified, then store a TIMESTAMP WITH TIMEZONE in one column, and the time zone name (ie. "America/Los_Angeles") in a second VARCHAR column, or elsewhere in your database. During an edit operation, use the time zone name to calculate the offset of the new value. It might be the same, or it may be different.
See also DateTime vs DateTimeOffset, which presents a similar argument for .Net and/or SQL Server.