Okay, so let's say that we have a calendar of thirteen months (here called "First Month," "Second Month," etc.; but this is just for our own tracking purposes--the Commonwealth would certainly never use such numbering), each of exactly 28 days, totaling 364 days. Because the solar year is roughly
365.25 days, this means that each year the calendar year will be "off" by an additional 1.25 days.
YEAR ZERO
First Month: New Moon (Dec 22--Winter Solstice) = New Year's Day Second Month: New Moon . . Thirteenth Month: New Moon (Nov 24)
YEAR ONE
First Month: New Moon (Dec 21). Month from Dec 21 to Jan 18.
Second Month: New Moon (Jan 19) = New Year's Day.
.
.
etc.
YEAR TWELVE
First Month: New Moon (Dec 6)
Second Month: New Moon (Jan 4) = New Year's Day
.
.
etc.
YEAR TWENTY-THREE (or year 22.4?)
First Month: New Moon (Dec 22--Winter Solstice) = New Year's Day . . etc.
(You can see why I insist that the Commonwealth not take numerical names for the months, since in Year One the year doesn't properly start until Second Month.)
Thus, in terms of our calendar, Commonwealth NYD falls between Dec 22 and Jan 19, the middle being somewhere around Jan 4.
While fuzzy and flexible, it is rather good for a neo-lunar calendar.
If the above is roughly true, and if feast days are likewise fuzzy, then feast days have the same 28 day range. Which can cause ambiguities at the borders of the seasons.
Plus, if that 23 year cycle implied above is valid, this could have a bearing on the text directly (because it seems likely that Severian is 23 years old when he becomes autarch).
=mantis=