Match fee periods properly.

src/cal-period.scm

@@ -53,6 +53,8 @@
   cal-month-in-period?
   cal-month-in-periods?
 
+  cal-month-find-period
+
   cal-day-in-period?
   cal-day-in-periods?
   
@@ -265,6 +267,19 @@
 	       #t
 	       (loop (cdr ps)))))))
 
+ ;; Returns true if given month is in at least one of the periods
+ ;; given. Defaults to current month.
+ (define (cal-month-find-period ps . ml)
+   (let ((m (if (null? ml)
+		(*current-month*)
+		(car ml))))
+     (let loop ((ps ps))
+       (if (null? ps)
+	   #f
+	   (if (cal-month-in-period? (car ps) m)
+	       (car ps)
+	       (loop (cdr ps)))))))
+
  ;; Checks whether given day belongs to day or month period
  (define (cal-day-in-period? p . dl)
    (let ((d (if (null? dl)