Function getActiveOffset

src/material/datepicker/multi-year-view.ts:425–433

(
  dateAdapter: DateAdapter<D>,
  activeDate: D,
  minDate: D | null,
  maxDate: D | null,
)

 * "startingYear" will render when paged into view.
 */
export function getActiveOffset<D>(
  dateAdapter: DateAdapter<D>,
  activeDate: D,
  minDate: D | null,
  maxDate: D | null,
): number {
  const activeYear = dateAdapter.getYear(activeDate);
  return euclideanModulo(activeYear - getStartingYear(dateAdapter, minDate, maxDate), yearsPerPage);
}

/**
 * We pick a "starting" year such that either the maximum year would be at the end