of *TIMER in the local timezone. */
extern struct tm *localtime (const time_t *__timer) __THROW;
-#ifdef __USE_POSIX
+#if defined __USE_POSIX || __GLIBC_USE (ISOC2X)
/* Return the `struct tm' representation of *TIMER in UTC,
using *TP to store the result. */
extern struct tm *gmtime_r (const time_t *__restrict __timer,
using *TP to store the result. */
extern struct tm *localtime_r (const time_t *__restrict __timer,
struct tm *__restrict __tp) __THROW;
-#endif /* POSIX */
+#endif /* POSIX || C2X */
/* Return a string of the form "Day Mon dd hh:mm:ss yyyy\n"
that is the representation of TP in this format. */
/* Equivalent to `asctime (localtime (timer))'. */
extern char *ctime (const time_t *__timer) __THROW;
-#ifdef __USE_POSIX
+#if defined __USE_POSIX || __GLIBC_USE (ISOC2X)
/* Reentrant versions of the above functions. */
/* Return in BUF a string of the form "Day Mon dd hh:mm:ss yyyy\n"
/* Equivalent to `asctime_r (localtime_r (timer, *TMP*), buf)'. */
extern char *ctime_r (const time_t *__restrict __timer,
char *__restrict __buf) __THROW;
-#endif /* POSIX */
+#endif /* POSIX || C2X */
/* Defined in localtime.c. */