John Paul I
De medietate lunae
From the half Moon
John Paul I's name was Albino Luciani which literally means "white light," as of the Moon. His diocese was Belluna, Italy which literally means "good Moon." His reign began on the phase of the half Moon, one day after its start. The term "half Moon" can also be interpreted as being symbolic of a short reign. He reigned for 34 days, starting from one day past the half Moon and ending just slightly less than a quarter past the next half Moon, but still within its phase. It has been reported that John Paul I privately predicted that his reign would be short and that he would be succeeded by Karol Wojtyla. Both predictions were correct. Incidentally, of the 100+ Cardinals in the August 1978 Conclave, Luciani and Wojtyla sat exactly across from each other in the Sistine Chapel. The official seating chart confirms this.
Thanks for that. I've forgotten where I saw it before!