Emacs supports the Hebrew calendar out of the box (alongside Julian, Islamic, Chinese, Mayan, Coptic, French Revolutionary etc etc) but I've never worked out ho

Emacs supports the Hebrew calendar out of the box (alongside Julian, Islamic, Chinese, Mayan, Coptic, French Revolutionary etc etc) but I've never worked out how make much use of it. Anyone have suggestions to get the festivals into Org Agenda, for example?