Hello, What I want to achieve is to be able to use the time functions in a multi-threaded program that can handle multiple timezones at the same time. Right now, this is impossible, because the notion of timezone is expressed through the environment. I was careful to re-use the existing code and not change existing functionality so the following routines are just an add-on. I modified tzcode 2010l to add the following functions (as defined in timeextra.h). First I expose an opaque timezone type: typedef struct __state *timezone_t; which is no other than the internal state. Then I provide a way to allocate the handle on per timezone name and to free it. const timezone_t tzalloc(const char *); void tzfree(const timezone_t); Note that the handle is const, because I might want to enhance this in the future to use reference counting instead of allocating a new one per invocation. Then I provide a way to return the two (dst and nondst) strings (like tzname[0], and tzname[1]) with: const char * tzgetname(const timezone_t, int); The following functions are also provided, which are like the _r counterparts only they have an extra timezone argument: struct tm * localtime_z(const time_t *, struct tm *, const timezone_t); char * ctime_z(const time_t *, char *, const timezone_t); time_t timelocal_z(struct tm *, const timezone_t); time_t mktime_z(struct tm *, const timezone_t); time_t time2posix_z(time_t, const timezone_t); time_t posix2time_z(time_t, const timezone_t); The changes to the source are minimal (the diffs are slightly larger because I made things use ansi prototypes and removed 'register '. I don't care about the names or the signatures much, just something I came up as a proof of concept. Here's example code: #include "timeextra.h" #include <stdlib.h> #include <stdio.h> int main(int argc, char *argv[]) { size_t i; char buf[60]; time_t t = time(NULL); timezone_t *tz = malloc(argc * sizeof(*tz)); for (i = 1; i < argc; i++) { tz[i] = tzalloc(argv[i]); if (tz[i] == NULL) err(1, "Cannot find timezone %s", argv[i]); } for (i = 1; i < argc; i++) { printf("[%s] [%s] %s", tzgetname(tz[i], 0), tzgetname(tz[i], 1), ctime_z(&t, buf, tz[i])); tzfree(tz[i]); } return 0; } Has anyone done this work or similar? Do you think others might want something like this? Are you interested in taking a look at the changes/incorporating them? Do you have any other suggestions? Best Regards, christos