>The Gregorian reformation was adopted by the Kingdom of Great Britain, including its possessions in North America (later to become eastern USA), in September 1752. As a result the September 1752 cal shows the adjusted days missing. This month was the official (British) adoption of the Gregorian calendar from the previously used Julian calendar. This has been documented in the man pages for Sun Solaris as follows. "An unusual calendar is printed for September 1752. That is the month when 11 days were skipped to make up for lack of leap year adjustments." The Plan 9 from Bell Labs manual states: "Try cal sep 1752." [0]
Some Orthodox Christians still use the Julian calendar, if only symbolically, so Christmas falls on January 7th and New Years on January 14th (Easter is a much different story: http://christianity.about.com/od/faqhelpdesk/qt/whyeastercha...). In theory, these dates should move farther and farther apart than just two weeks from the Gregorian calendar because the Julian calendar doesn't count leap years the same way.
For us Julian calendar folks, there's upsides and downsides. We get to celebrate Christmas late, but my kid will celebrate both (since my wife is of a different religion). And of course, Easter falls on Cinco de Mayo this year (but we had remember to buy enough egg coloring well in advance)! :)
>The Gregorian reformation was adopted by the Kingdom of Great Britain, including its possessions in North America (later to become eastern USA), in September 1752. As a result the September 1752 cal shows the adjusted days missing. This month was the official (British) adoption of the Gregorian calendar from the previously used Julian calendar. This has been documented in the man pages for Sun Solaris as follows. "An unusual calendar is printed for September 1752. That is the month when 11 days were skipped to make up for lack of leap year adjustments." The Plan 9 from Bell Labs manual states: "Try cal sep 1752." [0]
[0] http://en.wikipedia.org/w/index.php?title=Cal_(Unix)#Feature...