-the mode-line as the cursor moves, add `calendar-update-mode-line'
-to `calendar-move-hook'. Here is an example that has the Hebrew date,
-the day number/days remaining in the year, and the ISO week/year numbers:
+the mode-line as the cursor moves, add
+`calendar-update-mode-line' to `calendar-move-hook'.
+
+If nil, do not modify the mode line at all.
+
+Here is an example that has the Hebrew date, the day number/days
+remaining in the year, and the ISO week/year numbers: