+#define UNDEFINED_TIME 0
+#define TIMETOA_BUF 30
+
+/**
+ * @brief Display a date either in local or UTC time
+ *
+ * @param buf buffer where displayed time will be written to
+ * @param buflen buffer length
+ * @param time time to be displayed
+ * @param utc UTC (TRUE) or local time (FALSE)
+ *
+ */
+void timetoa(char *buf, size_t buflen, const time_t *time, bool utc);