How to set the time zone in Amazon EC2?

it should be no different than your desktop Ubuntu process. See here

1. SSH to your EC2 server

2. execute the following (to set timezone to Australia/Adelaide)

   $ echo "Australia/Adelaide" | sudo tee /etc/timezone
   Australia/Adelaide
   $ sudo dpkg-reconfigure --frontend noninteractive tzdata
   
   Current default time zone: 'Australia/Adelaide'
   Local time is now:      Sat May  8 21:19:24 CST 2010.
   Universal Time is now:  Sat May  8 11:49:24 UTC 2010.
   

Update

You can use tzselect utility to browse through. See here: http://manpages.ubuntu.com/manpages/precise/man1/tzselect.1.html

It's an interactive software. My Ubuntu (11.10) has it.

You could also refer this Wikipedia article

Brazil

Brazil/Acre
Brazil/DeNoronha
Brazil/East
Brazil/West

Another way of changing the time (This was done on an Amazon EC2 Linux instance)

Remove your localtime file

sudo rm /etc/localtime

Change Directory to ZoneInfo

cd /usr/share/zoneinfo

This folder contains all of the timezone information. You then just need to softlink to the appropriate zone.

Create a softlink to /etc/localtime

sudo ln -s /usr/share/zoneinfo/GB /etc/localtime

That will change your server timezone to GB