Merge pull request #13996 from poettering/utc-fix

accept UTC timezone explicitly, even if timezone data is missing

src/basic/time-util.c

@@ -1258,6 +1258,7 @@ int get_timezones(char ***ret) {
                 }
 
                 strv_sort(zones);
+                strv_uniq(zones);
 
         } else if (errno != ENOENT)
                 return -errno;
@@ -1277,6 +1278,10 @@ bool timezone_is_valid(const char *name, int log_level) {
         if (isempty(name))
                 return false;
 
+        /* Always accept "UTC" as valid timezone, since it's the fallback, even if user has no timezones installed. */
+        if (streq(name, "UTC"))
+                return true;
+
         if (name[0] == '/')
                 return false;