diff --git a/include/mbedtls/x509.h b/include/mbedtls/x509.h
index ac8ff9a..ef6b098 100644
--- a/include/mbedtls/x509.h
+++ b/include/mbedtls/x509.h
@@ -378,6 +378,19 @@
  */
 int mbedtls_x509_time_cmp(const mbedtls_x509_time *t1, const mbedtls_x509_time *t2);
 
+#if defined(MBEDTLS_HAVE_TIME_DATE)
+/**
+ * \brief          Fill mbedtls_x509_time with provided mbedtls_time_t.
+ *
+ * \param tt       mbedtls_time_t to convert
+ * \param now      mbedtls_x509_time to fill with converted mbedtls_time_t
+ *
+ * \return         \c 0 on success
+ * \return         A non-zero return value on failure.
+ */
+int mbedtls_x509_time_gmtime(mbedtls_time_t tt, mbedtls_x509_time *now);
+#endif /* MBEDTLS_HAVE_TIME_DATE */
+
 /**
  * \brief          Check a given mbedtls_x509_time against the system time
  *                 and tell if it's in the past.