Why is the timestamp generated by the PHP time() function so different from SQL datetime?
If I do a date('Y-m-d', time()); in PHP, it gives me the time now, as it should. If I just take the time() portion and do:
$now = time();
//then execute this statement 'SELECT * FROM `reservation` WHERE created_at < $now'
I get nothing. But hey, so if the value of $now was 1273959833 and I queried
'SELECT * FROM `reservation` WHERE created_at < 127395983300000000'
then I see the records that I have created. I think one is tracked in microseconds vs the other is in seconds, but I can't find any documentation on this! What would be the right conversion between these two?
The time() function doesn't return microseconds, so it should work if you're using the correct datatype. But you have 2 different datatypes right now, INT and a date field (could be DATE/DATETIME/TIMESTAMP). If you want to compare a date in the database to a timestamp as integer, you could use something like:
SELECT * FROM Tbl WHERE UNIX_TIMESTAMP(date) < $timestamp;
time() gives a Unix timestamp (seconds passed since 01-01-1970) - SQL wants to have timestamps in format YYYY-mm-dd hh-ii-ss which is done by date() - so if you don't want to call 2 PHP functions, just use $now = date("Y-m-d H:i:s") or, better, change your SQL query to created_at < NOW().
They're just 2 different ways of storing dates, each with their advantages and disadvantages. You can use MySQL's date field, or simply store unix timestamps in an INT field. You can also use:
SELECT UNIX_TIMESTAMP(field_name) FROM ...
to return a date field as a Unix timestamp.
The MySQL date field is human-readable and can store any date in the foreseeable future. However, it does not store timezone information which can cause serious issues if not handled correctly. Facebook had this problem a while back.
Unix timestamps store timezone information (since it's defined as the number of seconds since 12:00am January 1st 1970 UTC). Comparison operations are faster on integers, and PHP's time/date functions are designed to be used with Unix timestamps. However, Linux can only support dates from 1902 to 2038 and on Windows from 1970 to 2038. MySQL and architecture in general will switch to 64-bit integers long before 2038 arrives, but if you need to store dates that are in the distant future or past, Unix time isn't for you.
Related
I want to ask about changing a datetime value of PHP with datetime value from MySQL data.
I have try to do this at PHP:
$sitgl = date('Y-m-d', strtotime(2012-01-12));
$sijam = date('H:i:s', strtotime(13:00:00));
$awal = $sitgl.' '.$sijam;
$awal2 = date('Y-m-d H:i:s', strtotime($awal));
$debrangkat = strtotime($awal2);
And I'm trying to convert same datetime at MySQL like this (convert it to seconds):
SELECT date_start_book, time_start_book, (TO_DAYS(CAST(date_start_book AS DATE))*86400) + TIME_TO_SEC(CAST(time_start_book AS TIME)) FROM `t_request_queue` WHERE `request_id` = '1301-0087'
which is date_start_book value is 2012-01-12 and time_start_book value is 13:00:00
My question is: why the PHP code return value : 1357970400 but the MySQL value return 63525214800 ?
what must I do to make both of value is same? Is strtotime() not return a seconds or why?
First of all as others have suggested that php code is really hurting brain. You could make that Unix Timestamp in just one line. But to answer your real question. MYSQL TO_DAYS works different than PHP UNIX Timestamp
According to MySQL Website
Given a date date, returns a day number (the number of days since year 0).
mysql> SELECT TO_DAYS(950501);
-> 728779
mysql> SELECT TO_DAYS('2007-10-07');
-> 733321
TO_DAYS() is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it does not take into account the days that were lost when the calendar was changed. For dates before 1582 (and possibly a later year in other locales), results from this function are not reliable
And according to PHP Website timestamp is
Returns the current time measured in the number of seconds since the
Unix Epoch (January 1 1970 00:00:00 GMT).
And hence the difference in two values. Their starting point is way too distant from each other. MySQL starts from year 0 and PHP starts from year 1970.
Suggestion
I would suggest you save php's timestamp in mysql rather than a formatted date time. This will help you stay consistent and allow you to perform any date or time comparisons easily.
Finally, I change the PHP to datetime and at query I'm using ADD_DAYS to add a date with a seconds then I compare it with the PHP datetime result.
So many thanks to all contributor.
I have a PHP MySQL query that inserts some data into a MySQL database and it includes a timestamp.
Currently the INSERT query uses NOW() for the the timestamp column and it is saved in the database in the following format: 2012-07-24 13:13:02
Unfortunately for me the Server is not in my time zone and it is listed as America/Los_Angeles as shown print date_default_timezone_get();
I was hoping to do the following:
date_default_timezone_set('Europe/London');
$timefordbLondonEU = date('Y-m-d H:i:s', time());
and simply save into the database the $timefordbLondonEU in place of the NOW();
Is this a good way to save such data ?
Many Thanks,
Richard
[ADDED TEXT]
I changed the Type in the MySQL db to DateTime and did the following:
date_default_timezone_set('Europe/London');
$timefordbLondonEU = date('Y-m-d H:i:s', time());
It is working but Im still not getting the overall concept yet.
Assumptions based on your comments:
MySQL = Does not have a datatype UTC you simply use type INT.
Unix_TimeStamp() will save the current time or count? in UTC format such as 1343247227.
As UTC is a count from a common 0 point you can get any timezone from it. Assuming that you don't want a date before the reference 0 point in 1970.
My guess and lead on from what you have said is the best way to do it is save the time as UTC in an INT (1343247227) and then generate any time zones you want from there. Again assuming you don't need to store dates before the reference 0 point in 1970.
Equally why not store as datetime YYYY-MM-DD HH:MM:SS at a known timezone and then convert to UTC or other timezones. It all seems pretty messy =(
As #Petah said in the comments, store your times in UTC and covert them in the application as needed.
Unix timestamps are in UTC so I usually store my times in the database as timestamps. This saves the headache and confusion of first converting to UTC to insert, and then from UTC when selecting.
That is, make your time field an INT type, and use the function UNIX_TIMESTAMP() in MySQL when you insert, or get the timestamp from PHP using the time() function.
When you fetch the timestamp from the DB it will be in UTC, but when you display it in your PHP application using date(), it will display in the server timezone, or whatever you set with date_default_timezone_set.
Therefore the following two queries will work:
INSERT INTO `table` (id, time) VALUES(NULL, UNIX_TIMESTAMP());
// or
$time = time();
$query = "INSERT INTO `table` (id, time) VALUES(NULL, $time);
If you want to select it from the DB as a DATETIME, you can do this:
SELECT *, FROM_UNIXTIME(time) as dt FROM `table` WHERE 1
The resulting dt column will be in the format yyyy-MM-dd hh:mm:ss.
You can format the numeric timestamp in PHP using date()
If the PHP version you have is 64-bit, you aren't limited to the 1970 - 2036 range, PHP will support 64-bit timestamps, just make sure to use a BIGINT column in MySQL in that case.
Hope that helps.
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 trying to calculate the difference between a timestamp retrieved from a MySQL database and the current time.
Appreciate the help.
As mentioned by #RemoteSojourner, I got the current time in a UNIX timestamp format (which returns time in seconds), I got the timestamp from the DB (using an ORM) and converted that to a UNIX timstamp too and then subtracted the two timestamps.
$current_time = strtotime("now");
$last_access_time = strtotime($this->last_access);
$inactivity_duration = $current_time - $last_access_time;
This example makes the difference between now and one hour ago.
select timediff(now(), now() - interval 1 hour)
You can use the strtotime function to parse the MySQL timestamp into a Unix timestamp can be further parsed or formatted in the PHP date function.
Retrieve the datetime from mysql like this
SELECT UNIX_TIMESTAMP(`time_col`) FROM `tablename`...
AND compare it to time()
I need to make a timestamp to put into MySQL. The user is submitting a number (of weeks) I need to add that many weeks to today's date. What I am trying to do is calculate an end date of an ad that the user is submitting.
Any suggestions on how to do this? Thanks!
You can use strtotime to add time to a date - it takes a second argument that is the current time if none is passed. You can then pass that created time to the date function to create your timestamp:
$timestamp = date('Y-m-d H:i:s', strtotime('+10 weeks'));
I think DATE_ADD(CURDATE(), INTERVAL 2 WEEK) would add 2 weekss to the current date, for instance
If you want the ad to expire at a certain time of day you can use mktime:
$day = date("d") + ($weeks * 7);
mktime($hour,$minute,$second,$month,$day,$year);
Just to add, some would say that storing the UNIX time as a plain-old int field in the database is the more flexible and portable solution. Furthermore, inserts and updates happen faster because they only involve storing simple integers. It really depends on how much date manipulation you need to do at the database level. I tend to go for portability and do all my date calculations in PHP. To store the current timestamp, I would just insert into an integer column the output of:
strtotime('now');
or
time();
which both return the current (unix) timestamp. Date comparison thereafter can be done by fetching timestamps from the database and performing simple arithmetical operation, as trivial as:
if($tsFromDb > strtotime('+28 days')) {
echo 'it is the future, zombies!';
}
It really depends on what you're using dates for.