Now I have wrong timezone set on my server, so all the records in my MySQL database have timestamps different from the real by 4 hours. How do I update all the timestamps to match the real time?
For example, I have timestamp like 2014-06-28 20:34:29. I need it to become 2014-06-29 00:34:29.
Any help would be appreciated.
assuming your date field is named created_at
update <table> SET created_at = DATE_ADD(created_at,INTERVAL 4 HOUR)
From my android smartphone application (made by myself) I send a request to a server in Denver to save my location and time. The TIMESTAMP it saves is Denver's current time (9 hours difference from local time). Now after 16 hours from the last request I wrote in my php script
$query = "SELECT * FROM `tblLoc` WHERE datetime > (CURRENT_TIMESTAMP - 86400)";
so as if I wanted to show me past 24 hours....
THIS WAS MISTAKE!
$query = "SELECT * FROM `tblLoc` WHERE datetime > CURRENT_TIMESTAMP() - INTERVAL 24 HOUR";
in SQL 86400 != 24 HOUR!!!
You need to either change MySQL's time zone instead of PHP's, or change your query so that PHP provides the timestamp, like so:
$query = "SELECT * FROM tblLoc WHERE dateTime > (". time() ." - 86400)";
EDIT based on comment
UTC_TIMESTAMP() might be a good way to go, but make sure you are inserting/updating based on this same timestamp as well, and not based on CURRENT_TIMESTAMP().
UTC timestamp is based on GMT (Greenwich Mean Time) and is at GMT+0. Dallas is at GMT-6 and Asia/Jerusalem is at GMT+2. So UTC_TIMESTAMP() always means the current time in GMT timezone, regardless of what your current time zone setting is. CURRENT_TIMESTAMP() means the current time in your current timezone.
HOWEVER your results may still not be quite right. They may just look right for the moment, but may be off by a couple hours. But if you are inserting and updating based on CURRENT_TIMESTAMP and then selecting based on UTC_TIMESTAMP your results will not be correct.
I would suggest one of the following three solutions:
Switch your server's timezone to Asia/Jerusalem (make sure to restart MySQL to apply the change).
Set the timezone at the beginning of each script using 'SET time_zone = timezone;'.
Make a TZ environment variable with the correct timezone so that MySQL sets that timezone as the default on startup (again, make sure to restart MySQL).
This will be done with PHP.
I basically want to get the number of rows that were inserted 30 minutes ago.
I have a time field on my table which is type TIMESTAMP and on update it's set to CURRENT_TIMESTAMP.
The date is stored in this format:
2011-05-27 04:29:17
My query is supposed to look something like this, however i just can't do it
SELECT COUNT(*) FROM mytable WHERE UNIX_TIMESTAMP(time) < '.time().'-1800
Where time() is PHP's function that fetches the UNIX time.
What it should basically do is print me the number of rows inserted from now to 30 minutes ago, but i just can't seem to make it work.
Can somebody help?
Small edit:
Another problem i am seeing is that php's function time() displays the unix time which is UTC. The time stored in mysql is probably GMT i.e whatever my computer's time/timezone is set to.
You can easily get rows stored from now to 30 mins ago by simply using:
SELECT count(*) FROM mytable WHERE `time` >= DATE_SUB(UTC_TIMESTAMP, INTERVAL 30 minute)
Usage of UTC_TIMESTAMP is just an example if you're storing your date/time data as UTC_TIMESTAMP(), you can probably use NOW() if necessary, depends on what you're storing really.
**EDIT**
Removed bad pointers and fixed example :)
Do you really need your computer's timezone to be different than UTC? why not just set it to UTC & save yourself the confusion? If that doesn't work, just use dateadd() on mysql to convert your mysql timestamp to UTC when checking?
My suggestion would be to write a small function to convert the mysql timestamp to your PHP timestamp format & load it into mysql. Then all you need to do is to call tmstamp(time_stamp) instead of time_stamp in your query. You can do the reverse too i.e. Convert PHP's "30 minutes ago" timestamp to mysql format and rerun your query (probably easier).
Usually it's just a formatting issue. It's not standardized across programs.
I'm retrieving a unix timestamp from a DB and I want to check if this datetime has passed already.
I tried using an if statement to compare to time() but it always says the time has passed already.
What am I doing wrong?
EDIT: Just some more info..to determine am/pm I'm adding 12 to the hour if its PM before running it through mktime(). (Is this right?)
It's stored in the DB as int not as any datetime types.
Your PHP time could be affected by PHP's timezone. Use date_default_timezone_get() to find out what time zone you're in.
Make sure the timezones in the DB and PHP are the same, use NOW() function to fill the DB column with current timestamp (the column should be of datetime type), then you can get the timestamp using UNIX_TIMESTAMP() MySQL function which compares against PHP's time() just nice.
Alternatively, you can fill the DB column with something like
mysql_query("INSERT INTO your_table (your_date) VALUES (FROM_UNIXTIME(" . time() . "))")
That should work even with timezone discrepancies.
If you are using mktime to create a UNIX timestamp, PHP is using the timezone settings to interpret what you mean by the given parameters. It's possible that you should be using gmmktime. It depends on how the timestamps in the database are being created; I cannot say for sure without seeing more code and having a more detailed explanation.
I generally prefer to simply store all dates as DATETIME types in the UTC (GMT) timezone. It tends to be less confusing.
Just some more info..to determine am/pm I'm adding 12 to the hour if its PM before running it through mktime(). (Is this right?)
12 PM is hour 12.
1 PM is hour 13.
So you don't always add 12. (i.e., 12 Noon is the exception).
I'm using the America/New York timezone. In the Fall we "fall back" an hour -- effectively "gaining" one hour at 2am. At the transition point the following happens:
it's 01:59:00 -04:00
then 1 minute later it becomes:
01:00:00 -05:00
So if you simply say "1:30am" it's ambiguous as to whether or not you're referring to the first time 1:30 rolls around or the second. I'm trying to save scheduling data to a MySQL database and can't determine how to save the times properly.
Here's the problem:
"2009-11-01 00:30:00" is stored internally as 2009-11-01 00:30:00 -04:00
"2009-11-01 01:30:00" is stored internally as 2009-11-01 01:30:00 -05:00
This is fine and fairly expected. But how do I save anything to 01:30:00 -04:00? The documentation does not show any support for specifying the offset and, accordingly, when I've tried specifying the offset it's been duly ignored.
The only solutions I've thought of involve setting the server to a timezone that doesn't use daylight savings time and doing the necessary transformations in my scripts (I'm using PHP for this). But that doesn't seem like it should be necessary.
Many thanks for any suggestions.
I've got it figured out for my purposes. I'll summarize what I learned (sorry, these notes are verbose; they're as much for my future referral as anything else).
Contrary to what I said in one of my previous comments, DATETIME and TIMESTAMP fields do behave differently. TIMESTAMP fields (as the docs indicate) take whatever you send them in "YYYY-MM-DD hh:mm:ss" format and convert it from your current timezone to UTC time. The reverse happens transparently whenever you retrieve the data. DATETIME fields do not make this conversion. They take whatever you send them and just store it directly.
Neither the DATETIME nor the TIMESTAMP field types can accurately store data in a timezone that observes DST. If you store "2009-11-01 01:30:00" the fields have no way to distinguish which version of 1:30am you wanted -- the -04:00 or -05:00 version.
Ok, so we must store our data in a non DST timezone (such as UTC). TIMESTAMP fields are unable to handle this data accurately for reasons I'll explain: if your system is set to a DST timezone then what you put into TIMESTAMP may not be what you get back out. Even if you send it data that you've already converted to UTC, it will still assume the data's in your local timezone and do yet another conversion to UTC. This TIMESTAMP-enforced local-to-UTC-back-to-local roundtrip is lossy when your local timezone observes DST (since "2009-11-01 01:30:00" maps to 2 different possible times).
With DATETIME you can store your data in any timezone you want and be confident that you'll get back whatever you send it (you don't get forced into the lossy roundtrip conversions that TIMESTAMP fields foist on you). So the solution is to use a DATETIME field and before saving to the field convert from your system time zone into whatever non-DST zone you want to save it in (I think UTC is probably the best option). This allows you to build the conversion logic into your scripting language so that you can explicitly save the UTC equivalent of "2009-11-01 01:30:00 -04:00" or ""2009-11-01 01:30:00 -05:00".
Another important thing to note is that MySQL's date/time math functions don't work properly around DST boundaries if you store your dates in a DST TZ. So all the more reason to save in UTC.
In a nutshell I now do this:
When retrieving the data from the database:
Explicitly interpret the data from the database as UTC outside of MySQL in order to get an accurate Unix timestamp. I use PHP's strtotime() function or its DateTime class for this. It can not be reliably done inside of MySQL using MySQL's CONVERT_TZ() or UNIX_TIMESTAMP() functions because CONVERT_TZ will only output a 'YYYY-MM-DD hh:mm:ss' value which suffers from ambiguity problems, and UNIX_TIMESTAMP() assumes its input is in the system timezone, not the timezone the data was ACTUALLY stored in (UTC).
When storing the data to the database:
Convert your date to the precise UTC time that you desire outside of MySQL. For example: with PHP's DateTime class you can specify "2009-11-01 1:30:00 EST" distinctly from "2009-11-01 1:30:00 EDT", then convert it to UTC and save the correct UTC time to your DATETIME field.
Phew. Thanks so much for everyone's input and help. Hopefully this saves someone else some headaches down the road.
BTW, I am seeing this on MySQL 5.0.22 and 5.0.27
MySQL's date types are, frankly, broken and cannot store all times correctly unless your system is set to a constant offset timezone, like UTC or GMT-5. (I'm using MySQL 5.0.45)
This is because you can't store any time during the hour before Daylight Saving Time ends. No matter how you input dates, every date function will treat these times as if they are during the hour after the switch.
My system's timezone is America/New_York. Let's try storing 1257051600 (Sun, 01 Nov 2009 06:00:00 +0100).
Here's using the proprietary INTERVAL syntax:
SELECT UNIX_TIMESTAMP('2009-11-01 00:00:00' + INTERVAL 3599 SECOND); # 1257051599
SELECT UNIX_TIMESTAMP('2009-11-01 00:00:00' + INTERVAL 3600 SECOND); # 1257055200
SELECT UNIX_TIMESTAMP('2009-11-01 01:00:00' - INTERVAL 1 SECOND); # 1257051599
SELECT UNIX_TIMESTAMP('2009-11-01 01:00:00' - INTERVAL 0 SECOND); # 1257055200
Even FROM_UNIXTIME() won't return the accurate time.
SELECT UNIX_TIMESTAMP(FROM_UNIXTIME(1257051599)); # 1257051599
SELECT UNIX_TIMESTAMP(FROM_UNIXTIME(1257051600)); # 1257055200
Oddly enough, DATETIME will still store and return (in string form only!) times within the "lost" hour when DST starts (e.g. 2009-03-08 02:59:59). But using these dates in any MySQL function is risky:
SELECT UNIX_TIMESTAMP('2009-03-08 01:59:59'); # 1236495599
SELECT UNIX_TIMESTAMP('2009-03-08 02:00:00'); # 1236495600
# ...
SELECT UNIX_TIMESTAMP('2009-03-08 02:59:59'); # 1236495600
SELECT UNIX_TIMESTAMP('2009-03-08 03:00:00'); # 1236495600
The takeaway: If you need to store and retrieve every time in the year, you have a few undesirable options:
Set system timezone to GMT + some constant offset. E.g. UTC
Store dates as INTs (as Aaron discovered, TIMESTAMP isn't even reliable)
Pretend the DATETIME type has some constant offset timezone. E.g. If you're in America/New_York, convert your date to GMT-5 outside of MySQL, then store as a DATETIME (this turns out to be essential: see Aaron's answer). Then you must take great care using MySQL's date/time functions, because some assume your values are of the system timezone, others (esp. time arithmetic functions) are "timezone agnostic" (they may behave as if the times are UTC).
Aaron and I suspect that auto-generating TIMESTAMP columns are also broken. Both 2009-11-01 01:30 -0400 and 2009-11-01 01:30 -0500 will be stored as the ambiguous 2009-11-01 01:30.
I think micahwittman's link has the best practical solution to these MySQL limitations: Set the session timezone to UTC when you connect:
SET SESSION time_zone = '+0:00'
Then you just send it Unix timestamps and everything should be fine.
But how do I save anything to 01:30:00
-04:00?
You can convert to UTC like:
SELECT CONVERT_TZ('2009-11-29 01:30:00','-04:00','+00:00');
Even better, save the dates as a TIMESTAMP field. That's always stored in UTC, and UTC doesn't know about summer/winter time.
You can convert from UTC to localtime using CONVERT_TZ:
SELECT CONVERT_TZ(UTC_TIMESTAMP(),'+00:00','SYSTEM');
Where '+00:00' is UTC, the from timezone , and 'SYSTEM' is the local timezone of the OS where MySQL runs.
Mysql inherently solves this problem using time_zone_name table from mysql db.
Use CONVERT_TZ while CRUD to update the datetime without worrying about daylight savings time.
SELECT
CONVERT_TZ('2019-04-01 00:00:00','Europe/London','UTC') AS time1,
CONVERT_TZ('2019-03-01 00:00:00','Europe/London','UTC') AS time2;
This thread made me freak since we use TIMESTAMP columns with On UPDATE CURRENT_TIMESTAMP (ie: recordTimestamp timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP) to track changed records and ETL to a datawarehouse.
In case someone wonder, in this case, TIMESTAMP behave correctly and you can differentiate between the two similar dates by converting the TIMESTAMP to unix timestamp:
select TestFact.*, UNIX_TIMESTAMP(recordTimestamp) from TestFact;
id recordTimestamp UNIX_TIMESTAMP(recordTimestamp)
1 2012-11-04 01:00:10.0 1352005210
2 2012-11-04 01:00:10.0 1352008810
I was working on logging counts of visits of pages and displaying the counts in graph (using Flot jQuery plugin). I filled the table with test data and everything looked fine, but I noticed that at the end of the graph the points were one day off according to labels on x-axis. After examination I noticed that the view count for day 2015-10-25 was retrieved twice from the database and passed to Flot, so every day after this date was moved by one day to right.
After looking for a bug in my code for a while I realized that this date is when the DST takes place. Then I came to this SO page...
...but the suggested solutions was an overkill for what I needed or they had other disadvantages. I am not very worried about not being able to distinguish between ambiguous timestamps. I just need to count and display records per days.
First, I retrieve the date range:
SELECT
DATE(MIN(created_timestamp)) AS min_date,
DATE(MAX(created_timestamp)) AS max_date
FROM page_display_log
WHERE item_id = :item_id
Then, in a for loop, starting with min_date, ending with max_date, by step of one day (60*60*24), I'm retrieving the counts:
for( $day = $min_date_timestamp; $day <= $max_date_timestamp; $day += 60 * 60 * 24 ) {
$query = "
SELECT COUNT(*) AS count_per_day
FROM page_display_log
WHERE
item_id = :item_id AND
(
created_timestamp BETWEEN
'" . date( "Y-m-d 00:00:00", $day ) . "' AND
'" . date( "Y-m-d 23:59:59", $day ) . "'
)
";
//execute query and do stuff with the result
}
My final and quick solution to my problem was this:
$min_date_timestamp += 60 * 60 * 2; // To avoid DST problems
for( $day = $min_date_timestamp; $day <= $max_da.....
So I am not staring the loop in the beginning of the day, but two hours later. The day is still the same, and I am still retrieving correct counts, since I explicitly ask the database for records between 00:00:00 and 23:59:59 of the day, regardless of the actual time of the timestamp. And when the time jumps by one hour, I am still in the correct day.
Note: I know this is 5 year old thread, and I know this is not an answer to OPs question, but it might help people like me who encountered this page looking for solution to the problem I described.