Index: share/mk/bsd.sys.mk
===================================================================
--- share/mk/bsd.sys.mk
+++ share/mk/bsd.sys.mk
@@ -75,6 +75,7 @@
 CWARNFLAGS+=	-Wno-uninitialized
 .endif # WARNS >=2 && WARNS <= 4
 CWARNFLAGS+=	-Wno-pointer-sign
+CWARNFLAGS.clang+=	-Wdate-time
 # Clang has more warnings enabled by default, and when using -Wall, so if WARNS
 # is set to low values, these have to be disabled explicitly.
 .if ${WARNS} <= 6