Changing or Updating the time zone in Ubuntu Server

  There are quite a few reasons you may find that you need to change your time zone – for example, if you’re using a pre-made image for a virtual machine you may find that the default timezone is not set to your country. You can change the time manually, though there is a quick and easy way:  
sudo dpkg-reconfigure tzdata  
This reconfigures the tzdata (timezone data) package and runs you through a series of prompts asking which country/city you live in, and updates the time accordingly.   You can check the current system time with:  
date
  to verify that it worked!

Ubuntu: How to update PHP’s timezone

  We came across this one recently when setting up a Zabbix server, where the installation would not proceed until the PHP timezone was set. This is quite straightforward – using your favourite editor edit:  
/etc/php5/apache2/php.ini
  Look for the Module Settings section or search for:  
 date.timezone
  (in vi /date.timezone should get you there). Uncomment the line by removing the leading ; and then add in your desired timezone. For Sydney it would look like:  
[Date] ; Defines the default timezone used by the date functions ; http://php.net/date.timezone date.timezone = UTC+10
  Change UTC+10 to your desired timezone, save the file and restart Apache:  
sudo service apache2 restart
  Voila!