ABSTRACT
Easter is a feast, not a planet. You do not determine it to hours, minutes and seconds. Kepler
Since the start of the Christian era, the calendar has been one of the most fertile of all sources of theological controversy.1 The calendar was never merely a system of calibrating the year, capable of being perfected, for there was no single agreed natural standard against which it could be measured out. Rather, there were several reference standards: solar (the year), lunar (the month), and terrestrial (the day). Onto the framework created from these incommensurable natural quantities was laid a cycle of feasts and festivals which were human in origin, part civil and part religious. In the end, the choice of a calendar-and even the question of who had the authority to alter it-was a religious and cultural matter. In the Europe of the reformation and counter-reformation, calendar reform was bound to be controversial, and there was no purely scientific solution.
