calendar-islamic-date-string
calendar-islamic-date-string is an autoloaded Lisp function in `cal-islam.el
'.
(calendar-islamic-date-string &optional DATE)
String of Islamic date before sunset of Gregorian DATE.
Returns the empty string if DATE is pre-Islamic.
Defaults to today's date if DATE is not given.
Driven by the variable `calendar-date-display-form'.