diff --git a/Makefile b/Makefile
index 82156ba..18fd86c 100644
--- a/Makefile
+++ b/Makefile
@@ -5,6 +5,12 @@ CCFLAGS = --config apple2-asm.cfg
 
 TARGETS = prodos.mod.BIN ns.clock.system.SYS cricket.system.SYS test.BIN
 
+# For timestamps
+MM = $(shell date "+%m")
+DD = $(shell date "+%d")
+YY = $(shell date "+%y")
+DEFINES = -D DD=$(DD) -D MM=$(MM) -D YY=$(YY)
+
 .PHONY: clean all
 all: $(TARGETS)
 
@@ -15,7 +21,7 @@ clean:
 	rm -f $(TARGETS)
 
 %.o: %.s $(HEADERS)
-	$(CC65)/ca65 $(CAFLAGS) --listing $(basename $@).list -o $@ $<
+	$(CC65)/ca65 $(CAFLAGS) $(DEFINES) --listing $(basename $@).list -o $@ $<
 
 %.BIN %.SYS: %.o
 	$(CC65)/ld65 $(CCFLAGS) -o $@ $<
diff --git a/cricket.system.s b/cricket.system.s
index b2d6bf8..c167325 100644
--- a/cricket.system.s
+++ b/cricket.system.s
@@ -33,7 +33,7 @@ sys_start:
         sec
         bcs     relocate
 
-        .byte   $12, $1, $17   ; 12/1/17 - version date stamp
+        .byte   MM, DD, YY      ; version date stamp
 
 ;;; ------------------------------------------------------------
 ;;; Relocate this code from $2000 (.SYSTEM start location) to $1000
diff --git a/ns.clock.system.s b/ns.clock.system.s
index 68f94ed..0913fb9 100644
--- a/ns.clock.system.s
+++ b/ns.clock.system.s
@@ -33,7 +33,7 @@ sys_start:
         sec
         bcs     relocate
 
-        .byte   $11, $26, $17   ; 11/26/17 - version date stamp
+        .byte   MM, DD, YY      ; version date stamp
 
 ;;; ------------------------------------------------------------
 ;;; Relocate this code from $2000 (.SYSTEM start location) to $1000