When I manage server, there are many times the server have no right timezone as I want or customers want to change timezone of their server. There are a few different ways to change the default date and timezone within CentOS operating system for web servers with only command line / SSH access.

Here I only show you a simplest way to change timezone by tzselect

First you may need to remove the existing symlink before using tzselect

Code:
rm -f /etc/localtime

Then use tzselect to choose your timezone step by steps

Code:
tzselect
Please identify a location so that time zone rules can be set correctly.
Please select a continent or ocean.
 1) Africa
 2) Americas
 3) Antarctica
 4) Arctic Ocean
 5) Asia
 6) Atlantic Ocean
 7) Australia
 8) Europe
 9) Indian Ocean
10) Pacific Ocean
11) none - I want to specify the time zone using the Posix TZ format.
#? 2
Please select a country.
 1) Anguilla                       28) Haiti
 2) Antigua & Barbuda              29) Honduras
 3) Argentina                      30) Jamaica
 4) Aruba                          31) Martinique
 5) Bahamas                        32) Mexico
 6) Barbados                       33) Montserrat
 7) Belize                         34) Nicaragua
 8) Bolivia                        35) Panama
 9) Bonaire Sint Eustatius & Saba  36) Paraguay
10) Brazil                         37) Peru
11) Canada                         38) Puerto Rico
12) Cayman Islands                 39) Sint Maarten
13) Chile                          40) St Barthelemy
14) Colombia                       41) St Kitts & Nevis
15) Costa Rica                     42) St Lucia
16) Cuba                           43) St Martin (French part)
17) Curacao                        44) St Pierre & Miquelon
18) Dominica                       45) St Vincent
19) Dominican Republic             46) Suriname
20) Ecuador                        47) Trinidad & Tobago
21) El Salvador                    48) Turks & Caicos Is
22) French Guiana                  49) United States
23) Greenland                      50) Uruguay
24) Grenada                        51) Venezuela
25) Guadeloupe                     52) Virgin Islands (UK)
26) Guatemala                      53) Virgin Islands (US)
27) Guyana
#? 5

The following information has been given:

        Bahamas

Therefore TZ='America/Nassau' will be used.
Local time is now:      Sat Feb 25 10:28:19 EST 2012.
Universal Time is now:  Sat Feb 25 15:28:19 UTC 2012.
Is the above information OK?
1) Yes
2) No
#? y
Please enter 1 for Yes, or 2 for No.
#? 1

You can make this change permanent for yourself by appending the line
        TZ='America/Nassau'; export TZ
to the file '.profile' in your home directory; then log out and log in again.

Here is that TZ value again, this time on standard output so that you
can use the /usr/bin/tzselect command in shell scripts:
America/Nassau

Now let ‘s restart your server to make sure everything work well.

As a bonus, here I will show you what timezone are supported on your server.

This command will list all countries

Code:
ls /usr/share/zoneinfo/

Let ‘s say you are in Australia then use this to list all supported timezone area in Australia

Code:
ls /usr/share/zoneinfo/Australia/

In manual way you can make a shellscript like this:

Code:
ZONEINFO=Australia/Brisbane
rm -f /etc/localtime
ln -s /usr/share/zoneinfo/$ZONEINFO /etc/localtime

and just run it to change to your timezone.

Happy coding