Home Page
Archive > Posts > 2011 > All
Archive > Posts > 2011 > All

Warning: you do not have javascript enabled. This WILL cause layout glitches.

Setting the time zone through a numeric offset
They never make it easy

I had the need today to be able to set the current time zone for an application in multiple computer languages by the hourly offset from GMT/UTC, which turned out to be a lot harder than I expected. It seems most time zone related functions, at least in Linux, expect you to use full location strings to set the current time zone offset (i.e. America/Chicago).

After a lot of research and experimenting, I came up with the following results. All of these are confirmed working in Linux, and most or all of them should work in Windows too.

Language Format Note Format for GMT+5 Format for GMT-5
C Negate GMT-5 GMT5
Perl Negate GMT-5 GMT5
SQL Requires Sign +5:00 -5:00
PHP Negate, Requires Sign Etc/GMT-5 Etc/GMT+5

And here are examples of using this in each language. The “TimeZone” string variable should be a 1-2 digit integer with an optional preceding negative sign:
Language Example
#include <stdio.h> //snprintf
#include <stdlib.h> //setenv, atoi
#include <time.h> //tzset


char Buffer[10];
snprintf(Buffer, 10, "GMT%i", -atoi(TimeZone));
setenv("TZ", Buffer, 1);
use POSIX qw/tzset/;
SQL [Query string created via Perl]
$Query='SET time_zone="'.($TimeZone>=0 ? '+' : '').$TimeZone.':00"';
date_default_timezone_set('Etc/GMT'.($TimeZone<=0 ? '+' : '').(-$TimeZone));
New Laptop Cover
I'll try to post a picture when I get it integrated

As previously posted, I got a Macbook Pro last year and have been quite pleased with it. However, I got it for its hardware, and not its software (I run Linux and Windows on it generally). For reasons stated in the article ("glorified Fisher-Price activity centres for adults; computers for scaredy-cats too nervous to learn how proper computers work.") and the stereotypes as such for people that use them, I've really been wanting to get an overlay for the back of it, and my good friend Adam Shen has provided the cover art ^_^. So without further ado...

Laptop Hyrulean Productions Cover
SymLink Fix for Combining Android Project Versions
Yay again at NTFS symlinking :-)

Since I found out that NTFS now has semi-working native symlinks, I have updated the symlinking script used in the Combining an Android Project's Versions post. This script creates relative symlinks now through Perl instead of absolute hard links through Bash. It is as follows:

#Run this file to install links to shared files into all branches
use warnings;
use strict;

my $SharedDirectoryName="Shared";
my $NonProjectDirectories="^\\.(|/\\.git|/$SharedDirectoryName)\$"; #Non Project directories (., .git, $SharedDirectoryName)
my $IsWindows=(index(lc(`uname`), 'cygwin')!=-1);

#Create a symlink
sub MakeLink
	my ($LinkTarget, $LinkName, $IsWindows, $IsDirectory)=@_;

	#Create the target directory if it does not exist
	my $LinkDirectory=$LinkName;
	$LinkDirectory =~ s/\/[^\/]+$//;
	if(!-e $LinkDirectory) {
		print "Creating directory: $LinkDirectory\n";
		`mkdir -p "$LinkDirectory"`;
	#If the link already exists, issue a warning
	if(-l $LinkName) {
		print "Link already exists: $LinkName\n";

	#Create the relative symlink
	my $RelativePathFromLinkToTarget=('../' x ($LinkName =~ tr/\///)).$LinkTarget; #Determine the relative path between the link and its target
	my $Command;
	if(!$IsWindows) { #Create the Linux command
		$Command="ln -s \"$RelativePathFromLinkToTarget\" \"$LinkName\"";
	else #Create the Windows command
		#Replace /s in path with \s
		$RelativePathFromLinkToTarget =~ s/\//\\/g;
		$LinkName =~ s/\//\\/g;
		$Command='cmd /c mklink'.($IsDirectory ? ' /d' : '')." \"$LinkName\" \"$RelativePathFromLinkToTarget\"";

	print "$Command\n";

#Find required information from file searches
my @LocalBranches=grep(!/$NonProjectDirectories/, `find -maxdepth 1 -type d`); #Find version folders by ignoring Non Project directories
my @Files=split(/\n?^$SharedDirectoryName\//m, substr(`find $SharedDirectoryName -type f`, 0, -1)); shift @Files; #Find shared files

#Propagate shared files into different versions
foreach my $LocalBranch (@LocalBranches) {
	$LocalBranch=substr($LocalBranch, 2, -1); #Remove ./ and new line separator
	foreach my $File (@Files) {
		MakeLink("$SharedDirectoryName/$File", "$LocalBranch/$File", $IsWindows, 0);