(defun holiday-islamic (month day string)
"Holiday on MONTH, DAY (Islamic) called STRING.
-If MONTH, DAY (Islamic) is visible, the value returned is corresponding
-Gregorian date in the form of the list (((month day year) STRING)). Returns
-nil if it is not visible in the current calendar window."
+If MONTH, DAY (Islamic) is visible, returns the corresponding
+Gregorian date as the list (((month day year) STRING)).
+Returns nil if it is not visible in the current calendar window."
(let* ((islamic-date (calendar-islamic-from-absolute
(calendar-absolute-from-gregorian
(list displayed-month 15 displayed-year))))