-=head1 Notes On Dates And Spatial Relationships
-
-One of the nice things about having a calendar represented as a table
-accessible with grid coordinates is that some of the trickier date
-calculations become trivial. You can use packages such as I<Date::Manip>
-or I<Date::Calc> for these sort of things, but the algorithms are often
-derived from a common human activity: looking at a calendar on a wall.
-Say, for instance, that you are interested in "the third Friday of every
-month". If you are using a calendar with Sunday as the first day of the
-week, then Fridays will always be in column 5, starting from 0.
-Likewise, due to the fact that supressed headers are merely I<masked> in
-the actual table, the first row with dates in a calendar structure will
-B<always> be 2, even if the month, year, or day headers are disabled.
-The third friday of every month therefore becomes C<$c-E<gt>cell(2,5)>,
-regardless of the particular month. Likewise, the "nth dayname/week of
-the month" can always be mapped to table coordinates.
-
-The particulars of this grid mapping are affected if you have redefined
-what the first day of the week is, or if you have tweaked the table
-beyond the bounds of the calendar itself. There are methods that can
-help under these circumstances, though. For instance, in our example
-where we are interested in the 3rd Friday of the month, the row number
-is accessed with C<$c-E<gt>first_week_row + 2>, whereas the column
-number could be derived with C<$c-E<gt>last_col - 1>.