Subdividing the periods between the solstices and equinoxes.
Exact millisecond calculations of solstice/equinox periods by dividing the known quarters
obtained via a combination of the frink packages: secant and exactSeasons.
Subdivisions calculated between known quantities. For example, Spring 2015 is obtained directly from the frink calculation. Further subdivisions are derived by by dividing the known quarters of the year into approximately derived sections.