Found a solution here
http://cmanios.wordpress.com/2013/03/05/change-timezone-to-apache-server-and-php/
I have installed XAMPP in my Windows machine and I want to alter the timezone in Apache HTTP server, PHP module and MySql in order to see proper dates in server error.log, access.log and php_error_log output.
After some searching I found the solution:
1. In httpd.conf (\xampp\apache\conf\httpd.conf) , add the following line:
# Set timezone to Europe/Athens UTC+02:00
SetEnv TZ Europe/Athens
2. Edit php.ini (\xampp\php\php.ini) date.timezone value in [Date] section:
date.timezone = "Europe/Athens"
You can find the available PHP timezones in
http://php.net/date.timezone
3. In my.ini (\xampp\mysql\bin\my.ini) add or replace
default-time-zone = "Europe/Athens"
Now restart Apache HTTP and MySQL server and you are done!