Compare PHP server time with JavaScript time (client browser time) - php

Question

I am making a notification system which require the time since functionality.
I am using this script for timesince function(jQuery):
$.fn.updateSince = function(interval) {
var times = this.map(function(){ return { e: $(this), t: parseInt($(this).html()) }; });
var format = function(t) {
if(t > 86400) {
return Math.floor(t / 86400) + ' days ago';
} else if (t > 3600) {
return Math.floor(t / 3600) + ' hours ago';
} else if (t > 60) {
return Math.floor(t / 60) + ' minute ago';
} else if (t > 50) {
return '50 seconds ago';
} else if (t > 40) {
return '40 seconds ago';
} else if (t > 30) {
return '30 seconds ago';
} else if (t > 25) {
return '25 seconds ago';
} else if (t > 15) {
return '15 seconds ago';
} else if (t > 10) {
return '10 seconds ago';
} else {
return 'a few seconds ago';
}
}
var update = function(){
var now = new Date().getTime();
$.each(times, function(i, o){
o.e.html(format(Math.round((now - o.t) / 1000)));
});
};
window.setInterval(update, interval);
update();
return this;
}
The notifications are stored in MySQL database , each notification has a timestamp on it that is in this format: 2012-12-26 06:21:28
I use PHP strtotime and change it into UTC format when obtaining the time out of the database for each notificaiton item:(php)
$rows['time']= strtotime($temp_time." UTC");
When I pass it back to the client browser , using ajax. I will multiply the UTC time(from database) with 1000(javascript)
var time = parseInt(dbtime * 1000);
Then I can use the jQuery timesince function to turn it into time ago.
Problem:
My server time varies with client browser time.
How do I make them "compatible" with each other.
For example , a notification is made 2 hours ago according to client browser.
But PHP says its made 7 hours ago.
because client browser timezone is different with my server's
My logic is:
1. [PHP] Get current time , and use the notification time obtained from database to subtract with it.
database time - current time = time difference on server end
[PHP] Then we get a time difference. in this case 7 hours.
[PHP] How do i turn 7 hours into UTC format?
[Javascript] Send the current client browser time , also in UTC format to php script.
[PHP] client browser time - 7 hours(UTC?) = actual time of notification created for javascript use.
[PHP] Send back the results to Javascript , so now the time can be 2 hours ago on client browser's end.
How do I do this?
Just for info , UTC format is like(multiplied with 1000) : 1314952284779

Answer 1

Your logic could be:
Convert the notification time to UNIX timestamp using strtotime (or any similar function)
Use JavaScript Date function with this value (multiplied by 1000) to re-build the date
Use (new Date) - thatDate to calculate the difference
Convert to hours, minutes and seconds
The problem I see here is in the first step. You mention that the dates are stored as 2012-12-26 06:21:28 but what timezone does this date correspond to? If it is the same time as the server timezone then using strtotime("2012-12-26 06:21:28") is sufficient to generate correct timestamp.

Answer 2

i had the same problem to i store the ip of the user in the db and then convert that to location and get the timezone then uses this functionality. main reason of doing that is that i future you might me considering to get info about your user so that approach also gonna help then. You can use interval triggered function to run the code
j(document).ready(function () {
window.initial = 0;
window.setInterval(timeincrement, 60000);
function timeincrement() {
initial = initial + 60;
j('.coment').each(function () {
var timefromserver = j(this).find('input[type=hidden]').val();
timefromserver = parseInt(timefromserver);
if ((timefromserver / 216000) < 1) {
var secgone = timefromserver + initial;
var timeelasped = secgone / 60;
if (Math.floor(timeelasped) < 1) {
j(this).find('.lightgrey').text("Few seconds ago");
} else if (Math.floor(timeelasped) < 60) {
var innertext = timeelasped + " minutes ago";
j(this).find('.lightgrey').text(innertext);
} else if (Math.floor(timeelasped / 60) > 0) {
var hourgone = Math.floor(timeelasped / 60);
var innertext = hourgone + " hours ago";
j(this).find('.fdlightgrey').text(innertext);
}
}
});
}
});

Answer 3

For your info new Date().getTime() in JavaScript return UTC time, as far as the client clocks are right this means that you don't have to deal with different time zones of users, all you have to do is to provide the times from your server in UTC.
In PHP you should either use the gmdate function to create UTC time strings or simply don't format it and just ship the raw UNIX UTC time that you get from the time function.
In short UTC everywhere, then it works. As a bonus it works like daylight savings didn't exist.
You could also also do an adjustment to account for incorrect times on the client by sending a "now" time stamp when the page is first loaded, calculate how long ago that is on the client, and subtract this result from all future calculations. But given that practically all computers automatically adjust their clock to that of a time server it is quite rare that a computer clock is off by more than a few seconds.

Answer 4

if mysql data is UTC, i use Date.getTimezoneOffset() in JavaScript and apply it (offset is in minutes: -120 = GMT+2) to the time stored in mysql (obtained via php) when displaying historical time (when event happened) for a user.
RAMBLINGS:
also serves to compare current time with mysql data (never trust a user's clock, but their timezone is usually correct [except for frequent-flyers' laptops, ouch]).
i take care to tell the user what her timezone difference is (either by publishing GMT +/- XX or something like "HH:MM this should be your local time, please fix clock if it isnt") and asking them to confirm it, if necessary. your code will deal with the situation according to your relationship with user ("fix that clock, darnit" or "yes, hmmmm, would you like us to fix our clocks to fit paris time [though we are in argentina], madame?")