A simple data type for storing year-quarter dates in a human readable integer
format, e.g.: 3.Quarter of 2012 is stored as 20123. Supports simple
arithmetic operations such as + and - as well formatting.
Usage
date_yq(y, q)
is_date_yq(x)
as_date_yq(x)
Value
date_yq returns an object of type date_yq
is_date_yq returns TRUE or FALSE depending on whether its
argument is of type date_yq or not.
as_date_yq attempts to coerce its argument to date_yq