If you want to customize timezone to suit the needs of the particular geography which your websites is addressed to, you can switch the Timezone of your Joomla 3 website. This is a fairly easy step which done via the Joomla Globabl Configuration.
Go to System > Global Configuration
Click on the Server tab and go to Location Settings
Select the Server Time Zone you want your Joomla 3 website to have. As you can see below there is a whole list of server timezones you can have. Choose the timezone which you would have. This will change the time of articles published mostly, and other server times.