Specs

year_of_era(year()) :: {1..10000, era()}

Calculates the year and era from the given year.

The ISO calendar has two eras: the "current era" (CE) which starts in year 1 and is defined as era 1. And "before the current era" (BCE) for those years less than 1, defined as era 0.

Examples

iex> Calendar.ISO.year_of_era(1)
{1, 1}
iex> Calendar.ISO.year_of_era(2018)
{2018, 1}
iex> Calendar.ISO.year_of_era(0)
{1, 0}
iex> Calendar.ISO.year_of_era(-1)
{2, 0}