getdate+nts+rtc: avoid some coverity false positives

Modify the code to avoid making the following calls incorrectly reported
as important findings by the coverity static analyzer:

- memset() of size 0 at the end of an array
- mktime() on a struct tm that has uninitialized tm_yday

getdate.y

@@ -907,6 +907,7 @@ get_date (const char *p, const time_t *now)
   yyHour = tmp->tm_hour;
   yyMinutes = tmp->tm_min;
   yySeconds = tmp->tm_sec;
+  memset(&tm, 0, sizeof (tm));
   tm.tm_isdst = tmp->tm_isdst;
   yyMeridian = MER24;
   yyRelSeconds = 0;
@@ -943,7 +944,6 @@ get_date (const char *p, const time_t *now)
   tm.tm_hour += yyRelHour;
   tm.tm_min += yyRelMinutes;
   tm.tm_sec += yyRelSeconds;
-  tm.tm_wday = 0;
 
   /* Let mktime deduce tm_isdst if we have an absolute timestamp,
      or if the relative timestamp mentions days, months, or years.  */