diff --git a/libmisc/strtoday.c b/libmisc/strtoday.c
index d3218738..b0f15dd9 100644
--- a/libmisc/strtoday.c
+++ b/libmisc/strtoday.c
@@ -7,10 +7,6 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#if !defined(__GLIBC__)
-#define _XOPEN_SOURCE 500
-#endif
-
 #include <config.h>
 
 #include <ctype.h>