Glibc and musl both defines this macro. Glibc defines it for 64-bit time_t on 32-bit arch and for 64-bit architectures. Signed-off-by: Dmitry Chestnykh &lt;dm.chestnykh(a)gmail.com&gt; --- include/features.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/include/features.h b/include/features.h index 11b34205f..b5d4e79f2 100644 --- a/include/features.h +++ b/include/features.h @@ -437,4 +437,8 @@ # include <libc-internal.h> #endif +#if defined(__UCLIBC_USE_TIME64__) || __TARGET_ARCH_BITS__ == 64 +#define __USE_TIME_BITS64 1 +#endif + #endif /* features.h */ -- 2.44.0