Most years have 52 weeks, some have 53, according to ISO8601.



Task

Write a function which determines if a given year is long (53 weeks) or not, and demonstrate it.




dec31weekday ← {7|(⍵+⌊(⍵÷4)+⌊(⍵÷400)-⌊⍵÷100)}
isolongyear ← {(4 = dec31weekday ⍵) ∨ (3 = dec31weekday (⍵ - 1))}