The First Council of Nicaea, among other things, established a common formula for the date of Easter. Next month marks its 1,700th anniversary; Pope Francis and Ecumenical Patriarch Bartholomew of Constantinople were due to commemorate this milestone by meeting in the ancient city, now İznik, Turkey, though the Pope’s ill-health has almost certainly ruled it out. Nonetheless, both remain hopeful that, after 443 years of celebrating on (mostly) different dates, a shared observation can be restored between Catholic and Orthodox Christians – whose celebrations happen to coincide this year.