diff --git a/Days.Mod b/Days.Mod
index 914ff4d..ae5ac3c 100644
--- a/Days.Mod
+++ b/Days.Mod
@@ -1,8 +1,66 @@
 MODULE Days;
 
- TYPE Day* = RECORD END;
- 
- VAR sun*, mon*, tue*, wed*, thu*, fri*, sat* : Day;
+ TYPE 
+ Day* = POINTER TO DayDesc;
+ DayDesc = RECORD
+   next*, prev* : Day;
+ END DayDesc;
+ TYPE Week = ARRAY 7 OF Day;
 
+ VAR sun*, mon*, tue*, wed*, thu*, fri*, sat* : Day;
+ week: ARRAY 7 OF Day;
+
+ PROCEDURE Next*(d : Day): Day;
+ BEGIN
+   RETURN d.next
+ END Next;
+
+ PROCEDURE Prev*(d: Day): Day;
+ BEGIN
+   RETURN d.prev;
+ END Prev;
+
+ PROCEDURE inc(VAR j: SHORTINT);
+ BEGIN
+   IF j = 6 THEN
+     j := 0
+   ELSE
+     INC(j)
+   END
+ END inc;
+
+  PROCEDURE dec(VAR j: SHORTINT);
+ BEGIN
+   IF j = 0 THEN
+     j := 6
+   ELSE
+     DEC(j)
+   END
+ END dec;
+
+ PROCEDURE init(VAR w : Week);
+   VAR
+     i,j : SHORTINT;
+ BEGIN
+     i := 0;
+     REPEAT
+       j := i; inc(j);
+       w[i].next := w[j];
+       j := i; dec(j);
+       w[i].prev := w[j];
+     UNTIL i > 6;
+ END init;
+
+BEGIN
+  NEW(sun); NEW(mon); NEW(tue); NEW(wed); NEW(thu); NEW(fri); NEW(sat);
+  week[0] := sun;
+  week[1] := mon;
+  week[2] := tue;
+  week[3] := wed;
+  week[4] := thu;
+  week[5] := fri;
+  week[6] := sat;
+  
+  init(week);
 
 END Days.