Sign of the Times. In the thirteenth century, a Franciscan friar named Roger Bacon sent an appeal for calendar reform from England to the Pope in Rome. Bacon correctly calculated that the calendar was incorrect. His appeal was denied and the erroneous calendar continued to be used throughout Europe. Three centuries later, Pope Gregory XIII corrected the calendar in Catholic Europe by deleting ten days. Had the correction been ordered in Bacon's day, a papal adjustment of the calendar would have been accepted without question across Europe, but by 1582 Europe was religiously divided and Rome was no longer the focal point of European authority. Calendar reform in Europe was not universally embraced because Protestant Reformers and the Eastern Orthodox Church refused to accept the papal correction.

Promises of Trade and Riches. Sixty years after Bacon's death, a new and deadly disease, the bubonic plague, decimated Europe's population. Known...