leap_year = proc (year: int) returns (bool)
    return(year//4=0 & (year//100=0 | year//400=0))
end leap_year

weekday = proc (d: date) returns (string)
    own leapdoom: array[int] := array[int]$[4,1,7,2,4,6,4,1,5,3,7,5]
    own normdoom: array[int] := array[int]$[3,7,7,4,2,6,4,1,5,3,7,5]
    own days: array[string] := array[string]$[0:
        "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
        "Friday", "Saturday"
    ]

    c: int := d.year/100
    r: int := d.year//100
    s: int := r/12
    t: int := r//12

    c_anchor: int := (5 * (c//4) + 2) // 7
    doom: int := (s + t + t/4 + c_anchor) // 7
    anchor: int
    if leap_year(d.year)
        then anchor := leapdoom[d.month]
        else anchor := normdoom[d.month]
    end
    return(days[(doom+d.day-anchor+7)//7])
end weekday

start_up = proc ()
    po: stream := stream$primary_output()
    dates: array[date] := array[date]$
       [date$create( 1, 6,1800,0,0,0),
        date$create(29, 3,1875,0,0,0),
        date$create( 7,12,1915,0,0,0),
        date$create(23,12,1970,0,0,0),
        date$create(14, 5,2043,0,0,0),
        date$create(12, 2,2077,0,0,0),
        date$create( 2, 4,2101,0,0,0)]

    for d: date in array[date]$elements(dates) do
        stream$puts(po, date$unparse_date(d))
        if d<now()
            then stream$puts(po, " was on a ")
            else stream$puts(po, " will be on a ")
        end
        stream$putl(po, weekday(d))
    end
end start_up