+/* rfc3339 formats a cdtime_t time as UTC in RFC 3339 zulu format with second
+ * precision. */
+int rfc3339_zulu (char *buffer, size_t buffer_size, cdtime_t t);
+
+/* rfc3339nano formats a cdtime_t time as UTC in RFC 3339 zulu format with
+ * nanosecond precision. */
+int rfc3339nano_zulu (char *buffer, size_t buffer_size, cdtime_t t);
+
+/* rfc3339 formats a cdtime_t time as local in RFC 3339 format with second
+ * precision. */
+int rfc3339_local (char *buffer, size_t buffer_size, cdtime_t t);
+
+/* rfc3339nano formats a cdtime_t time as local in RFC 3339 format with
+ * nanosecond precision. */
+int rfc3339nano_local (char *buffer, size_t buffer_size, cdtime_t t);
+