diff --git a/common.mk b/common.mk
index 839eba3c13..3ee4ae05f2 100644
--- a/common.mk
+++ b/common.mk
@@ -1023,6 +1023,12 @@ yes-test-all: sudo-precheck
 sudo-precheck: PHONY
 	@$(SUDO) echo > $(NULL)
 
+update-man-date: PHONY
+	-$(Q) $(BASERUBY) -I"$(srcdir)/tool" -rvcs -i -p \
+	-e 'BEGIN{@vcs=VCS.detect(ARGV.shift)}' \
+	-e '$$_.sub!(/^(\.Dd ).*/){$$1+@vcs.modified(ARGF.path).strftime("%B %d, %Y")}' \
+	"$(srcdir)" "$(srcdir)"/man/*.1
+
 help: PHONY
 	$(MESSAGE_BEGIN) \
 	"                Makefile of Ruby" \
diff --git a/tool/vcs.rb b/tool/vcs.rb
index 4c0dcce4b0..e38d1cfc56 100644
--- a/tool/vcs.rb
+++ b/tool/vcs.rb
@@ -130,6 +130,11 @@ class VCS
     return last, changed, modified, *rest
   end
 
+  def modified(path)
+    last, changed, modified, *rest = get_revisions(path)
+    modified
+  end
+
   def relative_to(path)
     if path
       srcdir = File.realpath(@srcdir)