String	Produces
$calname	calendar name
$user	logged in user name, if any
$date	the displayed date
$year	year part of date
$month	month part of date
$day	day part of date
$categoryChooser	controls to hide/show events by category.

The category chooser displays checkboxes, one for each category; the checkboxes control whether events in that category are displayed or not. A number can be appended to "$categoryChooser" to have it display a table of checkboxes, instead of a single row. The number is how many columns to use in the table; e.g. "$categoryChooser_4" would display the categories in 4 columns.