[GitHub] [nuttx] acassis commented on pull request #9578: localtime: add tzreset function to force zone file reload

["acassis (via GitHub)" <gi...@apache.org>]

acassis commented on PR #9578:
URL: https://github.com/apache/nuttx/pull/9578#issuecomment-1599718486

   @michallenc talking about time and timezone, I think I found an issue on NuttX, it is generating 00:00 AM/PM (for US people 00:00 never exists, it is always 12:00 AM/PM).
   
   I'm using strftime with "%I" instead "%H" (see: https://stackoverflow.com/questions/1759455/how-can-i-account-for-period-am-pm-using-strftime)
   
   We can try this same program on Linux and NuttX:
   
   ```
   #include <time.h>
   #include <stdio.h>
   #include <stdlib.h>
   
   void print_time(time_t t) {
       char buf[256];
       strftime(buf, sizeof buf, "%H:%M %p", localtime(&t));
       printf("%s %s\n", getenv("TZ"), buf);
   }
   
   int main() {
       time_t t = time(NULL);
   
       setenv("TZ", "Europe/London", 1);
       print_time(t);
   
       setenv("TZ", "America/New_York", 1);
       print_time(t);
   
       return 0;
   }
   ```
   
   Testing on Linux with %H and then with %I:
   
   $ ./tztest 
   Europe/London 00:11 AM
   America/New_York 19:11 PM
   
   $ ./tztest 
   Europe/London 12:11 AM
   America/New_York 07:11 PM
   
   Testing on NuttX with "%H"
   
   nsh> hello
   Europe/London 00:00 AM
   America/New_York 00:00 AM
   nsh>
   
   Testing on NuttX with "%I"
   
   nsh> hello
   Europe/London 00:01 AM
   America/New_York 00:01 AM
   nsh>
   
   I suspect that strftime() also is ignoring the "TZ" environment variable.


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