Say I have multiple servers in multiple locations and I want to use MySQL's datetime type for the field date and I always want to have the field date have the UTC timestamp so I would execute a UTC_TIMESTAMP() when I add it to the database. Now say I want to have MySQL output the UNIX TIMESTAMP for it.
When I do this on Server A I get the string "2009-06-17 12:00:00" doing the UNIX_TIMESTAMP(STRING) on it gives me the number 1245240000 back. Which is 2009-06-17 12:00:00 in UTC time. Now I do the same thing on Server B.
I get the same string back since its the UTC string but when executing UNIX_TIMESTAMP(STRING) again I get back the wrong number back 1245232800 which is the UTC +2 time. How do I get around this? Should I do the convertion from string to timestamp on the PHP side?
G'day,
I'll ask the obvious here, did you check the date and time on both machines?
Edit: ... and the MySQL timezone was the same on both machines?
Update: Ok. The problem is in the fact that the timestamp string being passed into UNIX_TIMESTAMP is interpreted to be a value in the current timezone which is then converted back to UTC so, because you're in MEZ, two hours is subtracted to return it back to UTC so 7200 is subtracted from your timestamp when it is converted back to a Unix timestring.
Hence, the variation you see when using UNIX_TIMESTAMP() to convert is back to a Unix Epoch timestring.
BTW Shouldn't you be using a TIMESTAMP type for storing off your UTC_TIMESTAMPs instead of DATETIME type?
Update: Decoupling presentation time from stored time is definitely the way to go. You can then reuse the same data all around the world and only have to convert to and from local time when you are presenting the data to a user.
If you don't do this then you are going to have to store off the timezone when the timestamp was made and then go into all sorts of complicated permutations of having to work out if
the local timezone was in daylight saving time when it was stored,
what the difference is between the timezone at the time that the data was stored and the timezone where the data is to be presented.
Leaving it all storeed as UTC gets rid of that.
Most users won't be that happy if they have to work out the local time themselves based on the UTC time returned so systems usually convert to current local time for the user.
This is of course if the user wants the data expressed in local time which is usually the case. The only widely used system I can think of, off the top of my head, that stores and presents its data in UTC is system for air traffic control and flight plan management which are always kept in UTC (or ZULU time to be more precise).
HTH
cheers,
Have you tried doing this?
Execute this instructions together.
SET time_zone = 'UTC';
SELECT FROM_UNIXTIME(0), UNIX_TIMESTAMP('2009-06-17 12:00:00');
// 1970-01-01 00:00:00 1245240000
They only affect the client session, not the server configuration.
Related
I am getting data back from server like 2020-02-17 15:36:47 (with no time zone descriptor). This is a date that is generated BY the server and is actually in UTC time (the server's "local" time). However, it is stored as DateTime in MySQL without time zone information.
When I get this back from the server, I need to convert it to local time, but when I try to apply date pipe like dateVariable | date: 'short' : 'UTC' it actually adds time rather than takes it away (my local time is EST) - so I get 2/17/20, 8:36 PM where it should actually be 2/17/20, 10:36 AM.
I guess ths issue is that the client assumes the time coming from the server is already local time, and my pipe is converting it to UTC. In fact, I want to do the opposite - the server time is stored as UTC (even though it is not indicated as such in MySQL DateTime column), and I want to convert to EST (local) using the date pipe. I've searched about and not sure how to handle this outside of modifying what the server returns.
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 run the following MySQL query:
select unix_timestamp('2011-03-13 02:00:13'), unix_timestamp('2011-03-13 02:20:41'), unix_timestamp('2011-03-13 02:40:10');
And get the following odd result:
1300003200, 1300003200, 1300003200
I think there's some kind of daylight savings time going on here, though it still seems odd that all the values are magically the same.
I'd appreciate suggestions of how to prevent MySQL from doing daylight savings time things here, as well as some explanation as to why all the results are the same.
MySQL's behavior is correct, if your server's time zone "CDT" observes DST and you haven't set your session time zone to something different.
The UNIX_TIMESTAMP() function uses your session's time zone to interepret the value you give it.
The server interprets date as a value in the current time zone and converts it to an internal value in UTC.
...
Note: If you use UNIX_TIMESTAMP() and FROM_UNIXTIME() to convert between TIMESTAMP values and Unix timestamp values, the conversion is lossy because the mapping is not one-to-one in both directions. For example, due to conventions for local time zone changes, it is possible for two UNIX_TIMESTAMP() to map two TIMESTAMP values to the same Unix timestamp value. FROM_UNIXTIME() will map that value back to only one of the original TIMESTAMP values.
— http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_unix-timestamp
The timestamps in question did not exist in your time zone, so the server is giving you the most accurate possible answer... it's the time in UTC that the clock moved forward to, when the time moved forward, less than an hour prior to your datetime literals, which represent "times that never existed on that day" in your time zone.
If those timestamps are intended to be times in your local time zone, then the answer is that those are invalid values, since that time never happened where you are. On the other hand, if those timestamps are actually assumed to already be in UTC, then you're not getting the correct answer from UNIX_TIMESTAMP() on any query, because the time is being converted "from" a time zone it isn't actually expressed in.
If you SET ##TIME_ZONE = 'UTC'; and repeat the queries, you'll see what I mean, since UTC has no DST. This statment only sets your session's time zone, not the whole server.
If running SET ##TIME_ZONE = 'UTC'; gives you an error message such as ERROR 1298 (HY000): Unknown or incorrect time zone: 'UTC', it is likely that you have not populated MySQL with timezone information. As described here you can load this information by using the command:
mysql_tzinfo_to_sql /usr/share/zoneinfo/ | mysql -u root mysql -p
where the path /usr/share/zoneinfo may need to be replaced with a path specific to your system.
I am running MYSQL 4.1 database that stores call center data for our offices that operate in Europe.
My MYSQL database sits on a Windows 2003 server that's has its time zone set to Central European Time, which automatically adjusts to day light savings.
I want to able to produce a report that shows the log date and time in the correct time zone to our customers in Europe.
My database stores the log date / time of the call as a unix time stamp. So therefore the dates stored as UTC. I found MYSQL function that can easily adjust the log date time to a time zone of your choice.
It's called CONVERT_TZ. (More info:http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_convert-tz)
Example: SELECT CONVERT_TZ('2004-01-01 12:00:00','UTC','CET');
I tried to apply this to call that was logged on 01-06-2013 22:12
CONVERT_TZ(FROM_UNIXTIME(o.logdatex), 'UTC','CET') 'CET_L_DATETIME'
(logdatex is the unxtimestamp for when the call was logged)
To my confusion the statement returned - 2013-06-02 00:12:56.
I wanted to see what was returned when I just selected FROM_UNIXTIME(o.logdatex)
It returned the correct time! 2013-06-01 22:12:56 (This call was logged from our Amsterdam office)
My question is, does the FROM_UNIXTIME function automatically adjust the time from UTC according to what the time zone MYSQL server is set to? I cannot find any documentation that says it does.
My assumption this is because when you do FROM_UNIXTIME(o.logdatex) you convert from UTC to timezone of your server.
And now you date is not in UTC timezone. So in CONVERT_TZ(FROM_UNIXTIME(o.logdatex), 'UTC','CET') you don't convert from 'UTC' but from timezone of your server so you get a strange result for you.
Try to select FROM_UNIXTIME(o.logdatex) as a separate field in your query and compare results.
I am having this trouble in converting the exiting time string into a new Time object.
When I type this in console
t = Time.parse("8am")
2010-12-06 08:00:00 +0530
it gives back 08:00 as result as seen above.
But when I store this value using
business.start_time = t
business.save(:validate => false)
it stores 02:30 in MySql db.
This happens only when I store via console. When the same data comes from forms, it stores correctly as 08:00 in MySQL table. Is there any problem here. The time zone is set different from the default utc. Please help. what should i do.
I have to parse through all the records in a table and take one string attribute and convert it into its equivalent Time class value and store it in another attribute in the same table. I am writing a rake task for it. But while storing, I get 02:30 instead 08:00 (for example).
Be very careful with dates and MySQL. Datetime fields are stored as if they were strings in the db--so whatever Rails is sending in (check your log for the SQL) is what will be stored. I assume you're set to UTC in your environment.rb, so your Time object is being output in UTC as a string.
MySQL is poor (in my opinion) with respect to handling times in different zones and converting between zones.
I recommend you don't rush through your date handling. Always handle dates in your application and DB in UTC, and do any conversion to a specific timezone on a parsing (by specifying the timezone) or by formatting it in the view.
The time seems to be stored in UTC. Try setting the timezone correctly when starting your console session.