Showing posts with label Clavius. Show all posts
Showing posts with label Clavius. Show all posts

Oct 15, 2010

Last Week - Lost Week

If we lived in the 1500s, we would have skipped this past week. That is when the  calendars changed from Julian to Gregorian. The ten days between Oct. 4 and Oct. 15, 1582 had been declared out of existence by the pope.

By the mid-1570s, the Julian Calendar established in 45 B.C. was 10 days behind the real seasons of the year. The spring equinox was actually occurring about March 12 and Easter was falling too late in spring. All this happened because the Earth year is about 11 minutes short of the 365¼ days set by Julius Caesar. It’s really 365 days, 5 hours, 48 minutes, 46 seconds. If the drift kept up, Easter would eventually have been observed in the summer, and Christmas in the spring.

Pope Gregory XIII appointed a commission to tweak the Julian Calendar. Under the leadership of physician Aloysius Lilius and Jesuit astronomer Christopher Clavius, the commission consulted with scientists and clergy. After wrestling with various ideas for half a decade, the commission proposed eliminating three leap years in every 400 (years ending in 00, unless they are divisible by 400).

That would prevent further creep of the calendar against the seasons (except for a minuscule under-correction). But resetting the calendar so the equinox would come in late March needed a more drastic solution: 10 days would have to be wiped out of existence.

The commission sent its report to the pope Sept. 14, 1580. He issued a papal bull (formal proclamation issued by the pope, usually written in antiquated characters and sealed with a leaden bulla (seal)) on Feb. 24, 1582, declaring that the new calendar would go into force in October (when there were few holy days), and that 10 days would be skipped. The day after Oct. 4 would be called Oct. 15.

Only Italy, Spain and Portugal were fully ready by October.

Everyone’s birthday moved to a calendar date 10 days later, too, so 365 days would pass between one birthday and the next. Rents, interest, and wages had to be recalculated for a month that had only 21 days.

Most of Catholic Europe adopted the new, Gregorian calendar by 1584, but the old Julian calendar held on until 1752 in Britain and its colonies, and through 1918 in Russia, which used to celebrate its own October Revolution, in November. My, how time flies.