The %s specifier in strftime doesn't respect timezones.
Example:
#include <time.h>
#include <stdio.h>
int main() {
time_t t = 1234567890;
struct tm *tmp = gmtime(&t);
char output[200];
strftime(output, 200, "%s", tmp);
printf("%s\n",output);
return 0;
}
Run with a non UTC timezone. e.g. TZ=GMT+9
Output will be 1234600290 instead of expected 1234567890
Location in OpenBSD's libc:
http://anoncvs.estpak.ee/cgi-bin/cgit/openbsd-src/tree/lib/libc/time/strftime.c#n300
This bug also exists in FreeBSD's libc:
https://svnweb.freebsd.org/base/release/10.0.0/lib/libc/stdtime/strftime.c?view=markup#l312
Bug filed at https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=192016
This bug also exists in glibc:
http://fossies.org/dox/glibc-2.19/strftime__l_8c_source.html#l01133
Bug filed at https://sourceware.org/bugzilla/show_bug.cgi?id=17189
It does not occur in musl:
http://git.musl-libc.org/cgit/musl/tree/src/time/strftime.c?id=ac0acd569e01735fc6052d43fdf57f3a07c93f3d#n127
