Posix Timezone format

Guy Harris guy at alum.mit.edu
Fri Nov 14 00:30:47 UTC 2008

On Nov 13, 2008, at 3:05 PM, Louis Guindon wrote:

> My goal is to provide a user interface showing the information  
> derived from the TZ zone name. Based on the selected TZ zone name by  
> the user, I will assign the corresponding POSIX time zone string to  
> the Linux /tmp/TZ file. This way the local time will show up  
> properly for the user.

I.e., you're trying to make an application to give the user a list of  
time zones, let them select a time zone, and make that the system time  

Note that most if not all Linux systems use the Olson time zone  
database, so they are not required to have a POSIX time zone string as  
the time zone setting.

> However, I am having difficulty to find a reliable source for POSIX  
> time zone string representation for each defined time zone in the  
> Olson database.

There isn't necessarily a POSIX time zone string representation for  
each defined time zone.  POSIX time zone strings can't represent an  
arbitrary Olson-style time zone - they can't, for example, handle time  
zones where the rules change from year to year.

> I don’t know if there is an alternative way, but I am also wandering  
> if the TZ time zone name can used directly without going through the  
> POSIX representation of the time zone.

On many UN*Xes, it can (Solaris, most if not all other SVR4  
derivatives, most if not all Linux distributions,  
{Free,Net,Open,DragonFly}BSD, Mac OS X/iPhone OS).

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