Marco Russo and Alberto Ferrari grab a calendar:
Since its first release in 2010, DAX has had a set of time intelligence functions to simplify calculations like year-to-date, year-over-year, and so on. However, the calculations only supported the Gregorian calendar, without addressing similar requirements for other calendars, such as the 4-4-5, ISO, and many other non-Gregorian calendars. With the classic time intelligence, the columns of the Date table were unknown to the time intelligence functions, with the only exception of the date column in the Date table, typically Date[Date].
Click through to see what Marco and Alberto have come up with.