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I have a an application built with the jQuery based fullCalendar http://arshaw.com/fullcalendar/

My calendars events are loaded by an Ajax call that outputs JSON, it is configured to have Monday as the first day of the week and the default view is week.

It has been working fine, but I noticed that if I go forward to week 13 (beginning March 26th) the events are not loading properly. I figured straight away this must have something to do with daylight savings time changing which happens March 25th.

When I use the click on the next/prev buttons the calendar makes an ajax call using automatically generated start and end times, my php script on the background takes the start date calculates the week no and calls all the events in my database for that week.

For example on week 12 teh following variables are passed:

?start=1332115200&end=1332716400&_=1331237729591

PHP script:

$week_no = date('W', $_GET['start']);

Which works out as week no 12.

However the following week the variables passed are:

?start=1332716400&end=1333321200&_=1331238038820

$week_no = date('W',$_GET['start']); == 12 // same as last week

Nn further examination 

echo date("C",1332115200);    // == 2012-03-19T00:00:00+00:00
echo date("C",1332716400);    //2012-03-25T23:00:00+00:00 (1 hour short of being in week 13)

So obviously teh daylight change is causing the problem.

My question is, is this a problem with fullcalander or my PHP logic?

Bojangles
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Kevin Bradshaw
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  • What timezone is a) your computer b) the server/php set to? If there is a difference, that is pretty sure causing errors. Not necessarily this one, but there will be errors/problems in the future. You can't do really much about it as the fullCalendar depends on the client's clock. – Niko Mar 08 '12 at 22:26
  • oh really? that sucks. It should be possible to write code that will work in any timeszone at anytime. I kind of thought that was the point of a unix timestamp.. – Kevin Bradshaw Mar 09 '12 at 01:27
  • Yeah, but you need to do it right. fullCalendar does not pass UTC timestamps, but localized ones. That's what messing it all up. – Niko Mar 09 '12 at 10:21
  • Looking at the timezones as you suggested, both are set to UTC. fullCalendar is sending a timestamp that should be universal – Kevin Bradshaw Mar 09 '12 at 11:06

3 Answers3

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First of all: I don't know your code and your settings, so all I'm saying is pretty much a guess.

If you're systems are both set to UTC, there wouldn't (shouldn't) be a problem. The same goes for the correct usage of the JavaScript functions date.getUTC* (the fullCalendar does not use those) with a server set to UTC. But I think that only your server is actually set to UTC, while your computer is set to "Europe/London" or anything like that (that looks right now like UTC, because it is UTC+0 in the winter).

That all results in the following situation: fullCalendar tries to calculate the timestamp for e.g. 1st July 2012 00:00:00 - because the computer is set to a timezone where at that date a DST applies (UTC+0 in the winter, UTC+1 in the summer -> 1st of July = UTC+1) you will get a timestamp for that moment in time where it is 00:00:00 on the 1st of July IN LONDON. Because their time is one hour in front of the UTC, you will get 23:00:00 if you interpret that timestamp relative to UTC - and that is, what the server does.

A solution can be as simple as this:

<?php
date_default_timezone_set('Europe/London');

That way, the server should interpret the timestamp relative to UTC+0 if the corresponding date is in the winter and relative to UTC+1 if it is in the summer.

However, if the visitors timezone is set to something different e.g. "America/Los_Angeles", your application is still messed up and won't work as expected. The best way is usually to use UTC timestamps everywhere, but fullCalendar does not support that currently.

Niko
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  • Thank you for your input. Having worked on this for the last few days, I have come to much of the same conclusions. I have to say, it is extremely frustrating dealing with timezones and daylight savings etc. I have my application working in my house at this time, but the nature of time and geography suggests that its busted where ever you are! – Kevin Bradshaw Mar 10 '12 at 13:03
  • That is 100% the way I feel about this.. sticking to UTC is the best one can do, as long as that is possible. – Niko Mar 10 '12 at 14:33
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    Actually, reading up a bit more, fullCalendar (1.5+) does support UTC, with the use of 'Z' at the end of the date parameter. e.g. 2012-03-11T12:00:00.0000000Z is read as UTC. There is a gotcha though, UTC is considered as a timezone so ignoreTimezone needs to be set to false. http://code.google.com/p/fullcalendar/issues/detail?id=750 – Kevin Bradshaw Mar 10 '12 at 15:06
  • the above comment applies to fullCalendar1.5.2 – Kevin Bradshaw Mar 10 '12 at 15:49
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Maybe it depends on time zone, because Daylight Saving Time dates are different in different time zones. Make sure that the time zone which is set in php.ini file is the same as the time zone of your country.

Setting time zone is also possible with date_default_timezone_set function.

And here is list of supported timezones.
http://php.net/manual/en/timezones.php

Valeh Hajiyev
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0

Also check.... http://arshaw.com/fullcalendar/docs/event_data/ignoreTimezone/

it may also be of assistance

Mych
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