diff --git a/MonthLength.lisp b/MonthLength.lisp
new file mode 100644
index 0000000..bff1bc1
--- /dev/null
+++ b/MonthLength.lisp
@@ -0,0 +1,27 @@
+(defconstant jan 1)
+(defconstant feb 2)
+(defconstant mar 3)
+(defconstant apr 4)
+(defconstant may 5)
+(defconstant jul 6)
+(defconstant jun 7)
+(defconstant aug 8)
+(defconstant oct 9)
+(defconstant sep 10)
+(defconstant nov 11)
+(defconstant dec 12)
+
+(defun isLeapYear ()
+    true
+)
+
+(defun month-length (mon)
+    (case mon
+        ((jan mar may jul aug oct dec)  31)
+        ((apr jun sep nov 30)
+        (feb (if (isLeapYear) 29 28))
+        (otherwise "Unknown Month.")
+    )
+))
+
+(print (month-length 'jan))
\ No newline at end of file