I have a table named "students" where student information are stored. Last week, I added a column (type-datetime) to keep track students last login time.
It was working well when testing with localhost. So, I uploaded to hosting and after a few days, I noticed datetime are different with my local times. I called now() function in my code and it is inserting with server time (Seattle,USA Time). I tried to set it with my timezone.
SELECT ##session.time_zone;
SET time_zone = 'Asia/Rangoon';
SET time_zone = "+06:30";
SET ##session.time_zone = "+06:30";
although it is executed, it don't affect and inserting with server time like before.
My Question is how should I update my existing datetime value column to my respective timezone. Thanks and appreciating.
The best approach imho is to save all dates in UTC. Only at presentation time these times should be converted to the time and zone for the user.
Because you are using PHP, you can convert input into UTC and convert output to the desired timezone for presentation.
This makes it also easy and possible to show foreign visitors their own time on your website.
Related
I work on an existing project that stores dates to a MySQL DB. The dates are stored as UTC since all users so far were in GTM+0 and no conversion was needed.
I now need to modify the code so that users from other time zones can use the system. The users choose their timezone when they register to the system, so I have a table holding the timezone for each user.
I know I can use CONVERT_TZ() when I extract and store the dates, but to do so means to go through all the queries and add this function.
When I do:
SET ##session.time_zone:='+7:00';
select now();
The result changes with the timezone variable.
When I do:
SET ##session.time_zone:='+7:00';
select myDate from myTable;
The result stays the same, returning what is stored in the DB.
Is there any way I can change the connection string or is there a session variable I can use that will affect the queries without having to add CONVERT_TZ to every single query?
Edit: this is not a duplicate of Should I use field 'datetime' or 'timestamp'? since using timestamp means I need to change all the date field in the DB, while I try to change something more global so I will not have to do massive changes the Db fields or the code.
I am using DATETIME field to store my dates in MySQL. Without any timezone specified directly (there is just a datetime column)
But when timezone was changed on server MySQL updated all datetime columns according to new timezone.
Actually switching to EDT was the reason.
I don't need to recalculate my dates automatically - just want to store specific dates in it.
So even if tz changed manually to UTC from EST date should be same (from characters POV) if it was 2016-01-01 18:55 it should be same in any new tz..
I did not run any scripts\queries to update dates.
So it was performed either by MySQL itself or by server.
Need advice what I need to check to find and disable such feature.
Make sure you are using DATETIME and not TIMESTAMP
[From the MySQL documentation][1]:
MySQL converts TIMESTAMP values from the current time zone to UTC for storage, and back from UTC to the current time zone for retrieval. (This does not occur for other types such as DATETIME.)
You should also review this post (Duplicate):
Will changing a MySQL timezone change values of DateTime fields in a database?
I am sorry for the mess I brought
Just extended my query to grab some old dates - and it looks unchanged
So error defenetly in my code..
Anyway - thanks for your help
I'm working on a shared hosting so I don't have access to mysql configuration files.
The default timezone on that system is 'America/New_York' but I need to use UTC -5:00 for my databases.
Everytime I perform a query the timezone is set to UTC -5:00 like this:
SET time_zone='-5:00';
If I want the current time, SELECT NOW() returns the correct time and date, but when updating a table mysql uses the SYSTEM time and not the set timezone
UPDATE administradores SET ultimo_acceso=NOW() WHERE id=1
Why does those values are different? Shouldn't be the same time in both queries since I'm overriding the timezone?
I also tried with INSERT statement and that works fine.
If the ultimo_acceso field is of type TIMESTAMP, then the value is actually being stored as UTC and then converted back to the current time zone when you select the value back out. So you need to set the time zone again in the select statement.
If you are using a DATETIME data type, then the value you set should be persisted without conversion and you will get back exactly what you store - regardless of the timezone setting at time of select.
See the MySQL docs on this subject.
Note that DATETIME, DATE, and TIME fields will always return the exact time you placed into them, regardless of the value of the time_zone variable.
TIMESTAMP fields will automatically convert their values to the timezone specified by the time_zone variable.
I want to migrate our mysql server from shared hosting to local server.
Current server is in MST time zone and the values for the CURRENT_TIMESTAMP in databsse is stored as -7:00 GMT.
Now I want to move complete application on dedicated server in India. Also want to convert the date values stored in -7:00 GMT to +5:30 GMT.
I can accomplish this task of updating the dates by writing script to update the time, however I would like to know if is there any way I can do this from database itself (at time of import or while exporting itself)
mysql version 5.0.96-log. I am not getting option export timestamp in UTC.
When using mysqldump, set the flag: --tz-utc to force all timestamps to be exported as UTC. ( http://dev.mysql.com/doc/refman/5.1/en/mysqldump.html#option_mysqldump_tz-utc ). Note here --tz-utc is enabled by default. So you should have to do nothing: but test first :)
If just working with timestamps on the server you don't have to do anything to convert them, from the documentation on TIMESTAMP post MySQL 4.1 ( http://dev.mysql.com/doc/refman/4.1/en/timestamp.html ):
"values still are stored in UTC, but are converted from the current
time zone for storage, and converted back to the current time zone for
retrieval. As long as the time zone setting remains constant, you
get back the same value you store. If you store a TIMESTAMP value, and
then change the time zone and retrieve the value, the retrieved value
is different from the value you stored."
This is easy to test:
Save a timestamp to your table
Change the server's timezone
Retrieve it: the return value should reflect the new timezone.
So another option is you could just have both the servers set to the same timezone while doing the export / import, than set them back to the correct timezone(s) after it is complete, but note with MySQLDump this should not be necessary.
General syntax
SELECT DATE_ADD(<column_name>, INTERVAL HOUR);
for changing to UTC to MST
SELECT DATE_ADD(NOW(), INTERVAL 7 HOUR);
According to mysqltutorial
The values of the MySQL TIMESTAMP columns depend on connection’s time
zone. When insert values for MySQL TIMESTAMP columns, they are
converted to Universal Coordinated Time (UTC) from connection’s time
zone. When you select the value, the server converts it back from UTC
to the connection’s time zone so you have the same value that you
inserted.
Where does it get this info. from, the time the user sets his OS to or from some other method?
Javascript also has a way to do timezones but is more involved: onlineaspect
To specify connection-specific time you need to perform
SET time_zone = TZ;
Where TZ can be either numerical offset like +11:00 or name of timezone Asia/Vladivostok (for the latter you need to import timezones description. Ask your DBA to do so)
the example there is wrong, i just tested it. it returns the previously inserted timestamp, regardless of the timezone. mysql will always insert the time you specify, without modifying it. if you need timezone adjustment, you have to tell mysql explicit to do so; otherwise all times are assumed to be "local server time".