Locale Info+time zones

[eluser]chinedubond[/eluser]
hello,
I would like to know how to set the local info
such as time zones e.g GMT and data formats e.g dd/MM/YYYY
in codeigniter or php.
Thank you

[eluser]Yash[/eluser]
[url="http://ellislab.com/codeigniter/user-guide/helpers/date_helper.html"]Date Helper[/url]