-void tzset();
-struct tm *gmtime(), *localtime();
-char *asctime(), *ctime(), *timezone();
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+char *asctime __P((const struct tm *));
+clock_t clock __P((void));
+char *ctime __P((const time_t *));
+double difftime __P((time_t, time_t));
+struct tm *gmtime __P((const time_t *));
+struct tm *localtime __P((const time_t *));
+time_t mktime __P((struct tm *));
+size_t strftime __P((char *, size_t, const char *, const struct tm *));
+time_t time __P((time_t *));
+
+#ifndef _ANSI_SOURCE
+void tzset __P((void));
+#endif /* not ANSI */
+
+#if !defined(_ANSI_SOURCE) && !defined(_POSIX_SOURCE)
+char *timezone __P((int, int));
+void tzsetwall __P((void));
+#endif /* neither ANSI nor POSIX */
+__END_DECLS
+
+#endif /* !_TIME_H_ */