+/* format_zone reads time zone information from "extern long timezone", exported
+ * by <time.h>, and formats it according to RFC 3339. This differs from
+ * strftime()'s "%z" format by including a colon between hour and minute. */
+static int format_zone (char *buffer, size_t buffer_size, struct tm const *tm) /* {{{ */
+{
+ char tmp[7];
+ size_t sz;
+
+ if ((buffer == NULL) || (buffer_size < 7))
+ return EINVAL;
+
+ sz = strftime (tmp, sizeof (tmp), "%z", tm);
+ if (sz == 0)
+ return ENOMEM;
+ if (sz != 5)
+ {
+ DEBUG ("format_zone: strftime(\"%%z\") = \"%s\", want \"+hhmm\"", tmp);
+ sstrncpy (buffer, tmp, buffer_size);
+ return 0;
+ }
+
+ buffer[0] = tmp[0];
+ buffer[1] = tmp[1];
+ buffer[2] = tmp[2];
+ buffer[3] = ':';
+ buffer[4] = tmp[3];
+ buffer[5] = tmp[4];
+ buffer[6] = 0;
+
+ return 0;
+} /* }}} int format_zone */
+
+static int format_rfc3339 (char *buffer, size_t buffer_size, cdtime_t t, _Bool print_nano) /* {{{ */