diff --git a/calendar/generate_calendar.php b/calendar/generate_calendar.php
index da2445b..e3a16c7 100644
--- a/calendar/generate_calendar.php
+++ b/calendar/generate_calendar.php
@@ -18,12 +18,10 @@
     be valid as a LaTeX macro name (i.e., no spaces, no digits, no punctuation).
     The components of each period specification are:
     
-    start_date:     The date of the first day of the first week of the period.
-        
-    num_weeks:      The total number of weeks in the period, /including/ any
-                    breaks (e.g., 13 teaching weeks plus 1 week mid-semester
-                    break = 14 weeks).
-        
+	first_week:		The academic week number of the first week of the period.
+		
+	last_week:		The academic week number of the last week of the period.
+		
     break_weeks:    A list of breaks that occur during the teaching period.
                     Each is specified by the start (break_start) and end
                     (break_end) week. If a break is only one week long, then
@@ -33,10 +31,11 @@
                     
                     The list should ideally be in ascending order, but the
                     script doesn't assume this and sorts the list anyway. Weeks
-                    are numbered by absolute calendar week number (i.e., week
-                    1 is the first calendar week of the year). The date of the
-                    first Monday of the year is stored in $first_monday below
-                    (everything is Monday-indexed).
+                    are numbered by academic week number (i.e., week 1 is the
+                    first academic week of the year). The date of the first
+                    Monday of the year is stored in $first_monday below
+                    (everything is Monday-indexed). Note that academic week is
+                    normally the same as absolute calendar week.
 
     Example: