Well I know that this question may be asked many times but certainly I've few doubts In my mind, and by the way don't comment that what I've tried, I've tried many ways but am just asking what's the correct and easier way as there are many posts lingering out here with different suggestions for accomplishing these tasks, so I'll explode() my question into smaller questions...
So can you people just guide me where am going right or wrong as am sure many people are confused when it comes to date/time
1) Why/how to save time as UTC in MySQL using PHP?
Personally for this I post this using php $year/$month/$day and check the date using checkdate() in mysql date field. so is it ok or should I use timestamp and than explode the retrieved string on front end using php?
2) If I run server from India, should I record default time using date_default_timezone_set("Asia/Calcutta"); and than subtract and add time using php function or while posting only I should check users time zone selected from his user accound and accordingly set a condition kinda:
if(timezoneselected == +5.30) {
echo date_default_timezone_set("Asia/Calcutta");
} elseif(timezoneselected == +anytime) {
echo another country timezone
}
3) last question is how websites like gmail facebook etc manages time? I mean if they are saving datetime according to their server than how they show perfect posted time for each user, even gmail, if I send a mail to another user, my sent time and the person living in another country gets email at his printed local time I mean how we can do this, sorry am not able to explain you perfectly say this example,
facebook:
user from India posts, facebook shows posted 8 mins ago, 9mins ago, fine after sometime they show a real date, and that date is perfect according to the time I posted, however if a person from USA updates, say 8 mins ago 9mins ago on his profile but his original posted time is shown correctly to him, and even correctly to me?
sorry for this question but really this will help me understanding this date/time concept and will also be helpful to future users. Thank you!
Bottom line, you should store everything UTC
When you display times for a particular user, use a timezone of their choosing. Store the timezone of the user, like "Asia/Calcutta" and simply convert the time when displaying it using the date_default_timezone_set method.
I will attempt to answer your questions from the comment here.
You store everything UTC always. It is the baseline. When you display the times associated with anything you convert based on the user. If you want to display Posted 8 mins ago then you are taking the delta between the current UTC time and the UTC time associated with a post. If you send a message from user A (in India) to user B (in Los Angeles, USA) then you would store the message time in UTC. If user A is viewing it, the time would be converted to "Asia/Calcutta" and if user B is viewing it, the time would be converted to "America/Los_Angeles". Using UTC will make your life a lot easier. Trust me.
As described in MySQL Server Time Zone Support:
The current session time zone setting affects display and storage of time values that are zone-sensitive. This includes the values displayed by functions such as NOW() or CURTIME(), and values stored in and retrieved from TIMESTAMP columns. Values for TIMESTAMP columns are converted from the current time zone to UTC for storage, and from UTC to the current time zone for retrieval.
Therefore, if you use TIMESTAMP type columns, MySQL will handle timezone conversion for you automatically: just set the appropriate timezone for the session in its time_zone variable.
Related
I was wondering why should i need to store user's timezone as many suggested when I have two columns already in my db table local_datetime and utc_datetime which are used to show how long ago a comment was posted. I can use the utc_datetime and convert it to user's local time and the local_datetime helps me sorting results by a particular day for a user. So my question is, what is the purpose of storing timezone??
When you stored user's UTC time, it does not require any other parameters. That moment was same allover the world. If you want to know where that user came from, only then you need to store his/her timezone. Your use case seems to just calculate elapsed time you can do it by generating the time difference from stored UTC time and current UTC time.
I ran into trouble while dealing with date and time using php and mysql. I am trying to store local time of user's timezone as a timestamp on mysql db and would like it to convert back to normal date and time at the time of output.
This is the first time I am dealing with date and time.
As I understand: I can't rely on PHP's time() as it returns servers time according to server's timezone and the same case with mysql current_timestamp.
I can use the javascript to get user's local timezone and then can use date_default_timezone_set() for each session.
If I am doing right, now the confusion starts.
As you can understand the users will come from around the globe, so if two users (one from US and another from India) do something at the same time, will it show each others time as identical or it will show some difference? I mean it shouldn't show Indian user that the US user has done something few hours ago as the US user done at same time.
Please let me know if I don't understand these things properly.
What I want to achieve is, the output of the time should show in local time format. Ex: any time should show in IST format for Indian user and other country respectively.
Best way to achieve this is to store date in a database in a standard format (eg. GMT).
After getting user's timezone through javascript, you may convert date to user's timezone & display accordingly.
I am developing a chatting messenger of website application. For my concept, I avoid to use timezone.
When a user post a message, I use php to get my current server date/time and save it onto database.
To display the time of all messages to the user, I just need find out the different between server time and user's system time. Let's say the different is 3 hours, i just need use mysql to retrieve recorded server time from database then add it with 3, eg : $message-time-display = $server-time-of-message-posted + $different.
For this solution, although the user's computer time may be incorrect, it will not effect the time records that saved on my database. And it will display the correct time when the users have corrected their computer's time. Is this solution is reliable? If so, why there is none of people doing this? Why so many people are using GMT or timezone thingy? Maybe I miss some important issue?
One quick fix is not to show the exact time, rather the time elapsed. Ex: 2 minutes ago
And then...
Since you know the elapsed time you can substract that from the user's current time.
You can get the user current time with javascript.
var d = new Date();
var curr_hour = d.getHours();
var curr_min = d.getMinutes();
If you are writing an app that will only ever be on one server then it's ok to store time as your local server time. If your application will be deployed in many locations around the globe, then it makes better sense to store all times as UTC.
To my mind, user-provided times should be translated from user's timezone to UTC (or your server's timezone if it's your personal app) before being stored and should be translated back to the user's timezone when displayed.
So in your case, it should go something like this:
user action -> store UTC time in database
another user action -> compare current UTC time to stored UTC time and display difference.
If you're displaying timestamps, it should go like this:
user action -> store UTC time in database
user access -> retrieve stored UTC time and translate it to user's timezone. Display.
Your solution should work as long as the user has the time set correctly. That is the only problem actually. Why do you think no one is doing it ? I guess most of them do and only the lazy ones relies on GMT/EST times.
Hint: I saw the user time sent in tracking codes such as google's analytics javascript, probably for computing the difference you are taking about ;)
I need some guidance with one of my project requirements, I am developing an application which has to deal with various time zones.
Scenario:
User 1 is from India, so his time zone would be GMT+05:30
User 2 is from UK, so his time zone would be GMT+01:00
If the User 1 sends a message to User 2, I want to show the Message Sent/Received Time as per the user’s time zone. For example User 1 sends a message at 6:30 Indian time, when User 2 would view the message it would show as 2:00 UK time.
Here goes my question, whenever I save the message should I convert it to GMT+00, so all my base times stamps are the same and then later when I display the message, I convert it back to User specific time zone. Would this be complex? Is this the best way of doing this?
I like to get views for both saving and displaying, also when I should do the time conversion from optimization point of view. I would need do deal with any/all timezones.
I am developing this application with PHP and MySQL and I am aware of timezone conversion method come with both PHP and MySQL.
I am just trying to figure out the best way of doing this. Look forward to have all valuable suggestions.
Note : As of now I am not much worried with day/light savings.
Thanks
Ravi
When storing the messages, convert, use and store them in a DST neutral timezone - UTC or GMT, for example.
With them store the original timezone offset and the DST offset - this will help with business logic.
When displaying the message, use this data and convert to the local time.
See this question and answers for best practices regarding working with different time zones.
Here goes my question, whenever I save the message should I convert it to GMT+00, so all my base times stamps are the same and then later when I display the message, I convert it back to User specific time zone. Would this be complex? Is this the best way of doing this?
It is. The only caveat is to allow each user to specify their desired timezone to view times in (either as a preference or from their client system's settings or from user database).
I like to get views for both saving and displaying, also when I should do the time conversion from optimization point of view. I would need do deal with any/all timezones.
The best time to convert from client to GMT is in your "business" logic - basically, whatever logic you have which processes web form data. NOT on the database side.
The best time to convert from GMT to client for viewing is right before/in the presentation layer, e.g. when you're printing your HTML.
The reason is that this way, as little of the code as possible needs to worry about timezones.
NOTE This timezone related logic becomes VERY VERY complicated if/when you need to do any date-specific logic (e.g. aggregate based on date as opposed to merely print timestamp to the user).
When saving data to your database, use something like:
INSERT INTO TableName SET TheDateFile=UTC_TIMESTAMP()
And then, presuming that you allow each user to specify their own timezone, you will need to convert the date in your business logic (as mentioned by DVK)
Something like:
DATE_FORMAT(DATE_ADD(TheDateField, INTERVAL 2 HOUR) // or whatever value
I have not done this myself, but I guess it would be simple enough to store the hour interval as per the users timezone.
In any case if you deal with users which are on different timezones, you must separate the timezone from the date. I heard long time ago that wordpress did it the same way:
First step, determine timezone of the date
Second step, set the timezone of the date to GMT (+0)
Third step, store the timezone and the GMT date in two separate columns.
Anyway, if you need more informations, there's a post here
I have a social network site I have been working on for a couple years in PHP/MySQL, I am now re-buidling the whole site from scratch again though. This time around I would really like to add in the ability for users to set a timezone for times on my site.
So with that said, I am asking on a guide from start to finish of the steps I need to include to do this please. My old site used mysql datetime for all dates and times and it worked great but I read that it is best to use like a text filed and store all dates and times with UTC, can someone explain how I could do this? Would I still be able to use the now() function in php to save a time to the mysql?
Also I have seen the list that php can generate of all the timezones, the one where it shows like a million (not really) but I am wondering, would it be possible to show some sort of map with images or something and link to the main timezones?
Please any tips for setting a users timezone, I can do that part, but once I have a user's timezone saved and ready to use, how can I make sure the users see's the correct time and how do I save times in the correct time.
Sorry if this was confusing, any help would be great though, thanks.
When working with php, from my experience, it is the best to store timestamps, generated with time(), as an int in the database. While it may not be that easy to read them when looking at the database (as you cannot guess the actual date just from the number), but the timestamp is the most-native thing when working with dates in php.
To save each user's timezone, you can simply save the offset, in either hours, or better (as some timezones are half an hour off) in minutes. So for example my timezone offset would be +60 (UTC+1), while in America most will have something like -480 (UTC-8) or similar.
Then when displaying the times for a user, you just pick the timestamp (which is in UTC time) and the timezone offset and generate a readable date from it using the standard date() function for formatting.
For example:
<?php
$time = time(); // from database or time() for "now"
$offset = -480; // from database
// add the offset to the time you want to display and you have the user's time
echo date( 'd.m.Y H:i', $time + $offset * 60 );
?>
In addition you could then also store the formatting string (d.m.Y H:i) in the database, so that every user can pick his favorite format.
This topic gets complicated especially when you factor in daylight savings and the fact that your server will be in a different time zone from some of your members.
I suggest you take a look at some libraries out there that have been built to handle these issues. The PEAR package Date might be a good place to start. http://pear.php.net/package/Date
Basically, you would want your members to select a timezone for their profile. Then convert all times to UTC (to remove the offset of the server location) and store them in your database as a timestamp. When displaying the times, apply the timezone offset the member chose for themself (maybe with UTC as the default) as well as a date display format.