To set your desired timezone you need to copy your timezone file from /usr/share/zoneinfo directory to /etc/localtime file. Just change directories:

# cd /usr/share/zoneinfo

A directory listing reveals many regions and zones to choose from:

# ls   
Africa          Arctic          Australia       EET             Etc             HST             MST             Pacific         WET
America         Asia            CET             EST             Europe          Indian          MST7MDT         SystemV         posixrules
Antarctica      Atlantic        CST6CDT         EST5EDT         Factory         MET             PST8PDT         UTC             zone.tab

Listing the America directory with recursion looks like this:

# ls -R America/
Adak            Belem           Chicago         Edmonton        Guyana          Lima            Metlakatla      Noronha         Rankin_Inlet    St_Barthelemy   Tortola
Anchorage       Belize          Chihuahua       Eirunepe        Halifax         Los_Angeles     Mexico_City     North_Dakota    Recife          St_Johns        Vancouver
Anguilla        Blanc-Sablon    Costa_Rica      El_Salvador     Havana          Lower_Princes   Miquelon        Ojinaga         Regina          St_Kitts        Whitehorse
Antigua         Boa_Vista       Creston         Fortaleza       Hermosillo      Maceio          Moncton         Panama          Resolute        St_Lucia        Winnipeg
Araguaina       Bogota          Cuiaba          Glace_Bay       Indiana         Managua         Monterrey       Pangnirtung     Rio_Branco      St_Thomas       Yakutat
Argentina       Boise           Curacao         Godthab         Inuvik          Manaus          Montevideo      Paramaribo      Santa_Isabel    St_Vincent      Yellowknife
Aruba           Cambridge_Bay   Danmarkshavn    Goose_Bay       Iqaluit         Marigot         Montreal        Phoenix         Santarem        Swift_Current
Asuncion        Campo_Grande    Dawson          Grand_Turk      Jamaica         Martinique      Montserrat      Port-au-Prince  Santiago        Tegucigalpa
Atikokan        Cancun          Dawson_Creek    Grenada         Juneau          Matamoros       Nassau          Port_of_Spain   Santo_Domingo   Thule
Bahia           Caracas         Denver          Guadeloupe      Kentucky        Mazatlan        New_York        Porto_Velho     Sao_Paulo       Thunder_Bay
Bahia_Banderas  Cayenne         Detroit         Guatemala       Kralendijk      Menominee       Nipigon         Puerto_Rico     Scoresbysund    Tijuana
Barbados        Cayman          Dominica        Guayaquil       La_Paz          Merida          Nome            Rainy_River     Sitka           Toronto

America/Argentina:
Buenos_Aires    Cordoba         La_Rioja        Rio_Gallegos    San_Juan        Tucuman
Catamarca       Jujuy           Mendoza         Salta           San_Luis        Ushuaia

America/Indiana:
Indianapolis    Knox            Marengo         Petersburg      Tell_City       Vevay           Vincennes       Winamac

America/Kentucky:
Louisville      Monticello

America/North_Dakota:
Beulah          Center          New_Salem

I want America/Los_Angeles so I would type the following:

# cp America/Los_Angeles /etc/localtime

Verify your work with date:

# date
Fri Nov 13 16:12:30 PST 2015

Success.