Ceci n'est pas un calendrier Nephite
I don't know if it will show up on the wall of your Bishop's office, but there's a Nephite calendar displayed over at the always entertaining Meridian Magazine. At first I dismissed it as just another adventure in creative Mormon iconography, but lo and behold the author of the article also wrote the Encyclopedia of Mormonism entry on Book of Mormon Chronology (conveniently posted at his website) -- so I reached over and pulled it right off my bookshelf. Amazing. I don't know what that means to you, but to me it means that some bright Mormons actually believe this stuff! [My conclusion flows from two unremarkable propositions: first, the Encyclopedia editors were bright Mormons, not dull ones; and second, they wouldn't have put it in the Encyclopedia if they didn't believe it themselves.]
The Encyclopedia entry starts off with these two sentences: The Book of Mormon contains a chronology that is internally consistent over the thousand-year Nephite history . . . . However, its chronology has not been unequivocally tied to other calendars because of uncertainties in biblical dates and lack of details about the Nephite calendars. In other words, the Nephite chronology is fine until you try and tie it to real-world events we can date with some precision, then things suddenly become uncertain and inconsistent. I admire the author's frankness on this point -- I wish the purveyors of Nephite geography could be as forthcoming.
The big problem, you see, is that the Nephite chronology counts 600 years from the accession of Zedekiah (598 or 597 BC) to the birth of Christ (dated between 6 BC and 1 BC). So 600 Nephite years have to squeeze into between 597 and 591 Earth years. Solutions offered in the two articles include: (1) Nephite years are only 360 days. So what if seasons cycle around the calendar eight times in 600 years! (2) The Book of Mormon references to Zedekiah actually refer to one of Zedekiah's predecessors named Jehoiakim, who assumed what was left of the Judean throne in 608 BC. I think a historian would call this "creative use of historical documents."