The Standard Imperial Calendar in use throughout most of the Home Galaxy is based upon the Avalonian local calendar and consists of four-hundred-day years, divided into ten months: Unad, Diad, Triad, Tetrad, Pentad, Hexad, Heptad, Octad, Nonad, and Decad, each with 40 days, grouped into four, ten-day weeks. Dates are expressed either as <day>/<year>, as in 131/52013, or <day> <month>, <year>, as in 11 Triad, 52013.