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List of all times zones in R

4 messages · Maithula Chandrashekhar, Joe King, Brian Ripley +1 more

Maithula Chandrashekhar
# 
Hi all, in R I have?Sys.timezone() function to get the current working
Time zone. However I want to have a vector to get the list of all
available time zones, like say, LETTERS gives me all letters. Is there
any function like that?

Thanks in advance,
Joe King
# 
Type in letters into command prompt
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r"
"s"
[20] "t" "u" "v" "w" "x" "y" "z"

Joe King
206-913-2912
jp at joepking.com
Ad astra per aspera ? ?Through hardships to the stars?


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Maithula Chandrashekhar
Sent: Sunday, January 30, 2011 10:08 PM
To: r-help at r-project.org
Subject: [R] List of all times zones in R

Hi all, in R I have?Sys.timezone() function to get the current working
Time zone. However I want to have a vector to get the list of all
available time zones, like say, LETTERS gives me all letters. Is there
any function like that?

Thanks in advance,

______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Brian Ripley
#
On Mon, 31 Jan 2011, Maithula Chandrashekhar wrote:

            

      
      
      
    

        
No, because the timezones are not 'in R': they are in your OS (as 
?Sys.timezone stresses).  Many OSes do not even has a function to give 
you their name for the current timezone, let alone all others.  Note 
too that an OS often has many names for a single time zone.

Despite the posting guide, you have given us no details of your 
system.  On Windows, the help page says

   A file listing most known time zones can be found at
   R_HOME/share/zoneinfo/zone.tab.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      David Winsemius
    

    

      
      #
    

  


  

      
On Jan 31, 2011, at 1:07 AM, Maithula Chandrashekhar wrote:

        

            

      
      
      
    

        
Only on some systems.

            

      
      
      
    

        
On a Mac (10.5.8)  the timezone information is in /usr/share/timezone/  
which also has a file named "zone.tab"

This is the header of that file:
 > readLines("/usr/share/zoneinfo/zone.tab")
   [1] "# <pre>"
   [2] "# @(#)zone.tab\t8.28"
   [3] "# This file is in the public domain, so clarified as of"
   [4] "# 2009-05-17 by Arthur David Olson."
   [5] "#"
   [6] "# TZ zone descriptions"
   [7] "#"
   [8] "# From Paul Eggert (1996-08-05):"
   [9] "#"
  [10] "# This file contains a table with the following columns:"
  [11] "# 1.  ISO 3166 2-character country code.  See the file  
`iso3166.tab'."
  [12] "# 2.  Latitude and longitude of the zone's principal location"
  [13] "#     in ISO 6709 sign-degrees-minutes-seconds format,"
  [14] "#     either +-DDMM+-DDDMM or +-DDMMSS+-DDDMMSS,"
  [15] "#     first latitude (+ is north), then longitude (+ is east)."
  [16] "# 3.  Zone name used in value of TZ environment variable."
  [17] "# 4.  Comments; present if and only if the country has  
multiple rows."
  [18] "#"
  [19] "# Columns are separated by a single tab."
  [20] "# The table is sorted first by country, then an order within  
the country that"
  [21] "# (1) makes some geographical sense, and"
  [22] "# (2) puts the most populous zones first, where that does not  
contradict (1)."
  [23] "#"
  [24] "# Lines beginning with `#' are comments."
  [25] "#"
  [26] "#country-"
  [27] "#code\tcoordinates\tTZ\t\t\tcomments"
  [28] "AD\t+4230+00131\tEurope/Andorra"
snipped the remaining 400 lines

In addition in that directory, there are separate subdirectories for  
each timezone and the number of such entries exceeded the number of  
lines in zone.tab. Attached is a file with the names of the  
subdirectories with the common stem removed produced by with this code  
acting on a pasted screen scrape of a terminal session:

 > TZlist <- strsplit(gsub("/usr/share/zoneinfo/", "", gsub("\\\n",  
",", txt)), ",")
 > write.table(TZlist, file="TZlist.txt")

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This is its tail:
[570] "US/Alaska"
[571] "US/Aleutian"
[572] "US/Arizona"
[573] "US/Central"
[574] "US/East-Indiana"
[575] "US/Eastern"
[576] "US/Hawaii"
[577] "US/Indiana-Starke"
[578] "US/Michigan"   # my birth state, its timezone rules seem to  
change with every election.
[579] "US/Mountain"
[580] "US/Pacific"
[581] "US/Samoa"
[582] "UTC"
[583] "Universal"
[584] "W-SU"
[585] "WET"
[586] "Zulu"     # which I seem to remember is a synonym for UTC

Sys.timezone doesn't actually produce useful information in all cases  
(and this is documented behavior).

 > Sys.timezone()
[1] ""
 > Sys.getenv("TZ")
TZ
""

You can change the timezone on a Mac (and probably on other systems)  
with Sys.setenv():

 > Sys.time()
[1] "2011-01-31 08:35:17 EST"
 > Sys.setenv("TZ"="US/Samoa")
 > Sys.time()
[1] "2011-01-31 02:35:52 SST"
 > Sys.setenv("TZ"="US/Eastern")
 > Sys.time()
[1] "2011-01-31 08:37:07 EST"