Index: firmware/include/timefuncs.h
===================================================================
--- firmware/include/timefuncs.h	(revision 13700)
+++ firmware/include/timefuncs.h	(working copy)
@@ -27,6 +27,8 @@
 struct tm *get_time(void);
 int set_time(const struct tm *tm);
 bool valid_time(const struct tm *tm);
+#if CONFIG_RTC
 time_t mktime(struct tm *t);
+#endif
 
 #endif /* _TIMEFUNCS_H_ */
Index: firmware/common/timefuncs.c
===================================================================
--- firmware/common/timefuncs.c	(revision 13700)
+++ firmware/common/timefuncs.c	(working copy)
@@ -131,6 +131,7 @@
 #endif
 }
 
+#if CONFIG_RTC
 /* mktime() code taken from lynx-2.8.5 source, written
  by Philippe De Muyter <phdm@macqel.be> */
 time_t mktime(struct tm *t)
@@ -165,3 +166,4 @@
     result += t->tm_sec;
     return(result);
 }
+#endif