In the Almost Decimal Calendar, the year is divided either into 5 quinters (alias quintals) or into 10 months, each of which contains a whole number of weeks in a pattern of 10:11 for the former and 5:5:6:5 for the latter. That means each quinter is split into two months and a year has 10 months. The leap week is appended to the last quinter and month. The ISO-like date format is ±YYYY-Q-W-D or ±YYYY-MM-W-D and ±YYYY-Q-M-W-D The calendar is compatible with that standard as far as possible, e.g. weeks begin on Monday.