[LK - This article is for J2.5 but can be easily adapted to J3.xx]
By default, logs written to Joomla's logs/error.php file are written in UTC time. There may be instances however when you need for Joomla to log using the server's timezone and not UTC time. In this tutorial, we'll show you how to update a Joomla 2.5 core file to adjust the timezone in logs/error.php
Please note: If you are simply trying to adjust the timezone in Joomla 2.5, please see How to change the timezone in Joomla 2.5. This article (the one you're looking at now) focuses on changing the timezone that Joomla uses when writing to error logs.
To change the timezone in Joomla's logs/error.php log file:
Step 1.Use your favorite file editor and open for edit libraries/joomla/log/entry.php
Step 2. At line 98, you will see the following code:
// Get the date as a JDate object.
$this->date = new JDate($date ? $date : 'now');
Adjust this code so that it looks similar to the following:
// Get the date as a JDate object.
// $this->date = new JDate($date ? $date : 'now');
$this->date = new JDate(date("Y-m-d H:i:s"));
Step 3.Save the file, and you're done! Joomla's logs/error.php will now record errors with your server's current timezone.