with javascript_semantics
function week_number(integer y,m,d)
    integer doy = day_of_year(y,m,d),
            dow = day_of_week(y,m,d),
            week = floor((doy-dow+10)/7)
    return week
end function
--/* -- or: (same results)
constant Thursday = 4
function long_year(integer y)
    return day_of_week(y,1,1)=Thursday
        or day_of_week(y,12,31)=Thursday
end function
--*/

for c=20 to 22 do
    sequence long_years = {}
    integer century = (c-1)*100
    for year=century to century+99 do
        if week_number(year,12,28)=53 then
--      if long_year(year) then
            long_years &= year
        end if
    end for
    printf(1,"Long years in the %d%s century:%v\n", {c,ord(c),long_years})
end for