A longer piece is on tap for later in the day (or tomorrow). But meantime, today, February 24th, marks the 425th Anniversary of Pope Gregory XIII's adoption of the calendar (in 1582) that bears his name: The Gregorian Calendar.
You might note that the name sounds familiar. It's the calendar that most of the world uses, notable for being a SOLAR calendar. Most calendars are lunar (since it's a lot easier to track the "moonth" than the solar year). For some interesting details, take a look at Wikipedia:
and, perhaps, the Galileo Project at Rice University:
The "Sort of" part? Well, ten days were dropped in October of 1582, to correct the drift of the Vernal Equinox that had built up. So, February 24th 1582 isn't EXACTLY the 425th Anniversary, but, really, it's as good a day as any to commemorate the fixing of the Julian Calendar (after Julius Caesar, who implemented it). See: