Template:Year in US territory category/doc

Purpose
This template is intended to be used on year in US territory categories (for example, Category:1778 in the Northwest Territory or Category:1827 in Florida Territory). It creates a "timeline" style table of links to categories for adjacent years before or after it in the same decade (see example below).

Syntax
No parameters are needed, and none are available.

Error-checking
The template checks that the page:
 * 1) is a category
 * 2) has a title of the form "YYYY in Foo"

If either of those conditions is not met, an error message is displayed and no other output is generated, but the page is added to a tracking category:
 * Category:Errors reported by other category header templates (population: )

Note that this category is also used by many other category header templates