BEGIN
    INTEGER WIDTH, YEAR;
    INTEGER COLS, LEAD, GAP;
    TEXT ARRAY WDAYS(0:6);
    CLASS MONTH(MNAME); TEXT MNAME;
    BEGIN INTEGER DAYS, START_WDAY, AT_POS;
    END MONTH;
    REF(MONTH) ARRAY MONTHS(0:11);
    WIDTH := 80; YEAR := 1969;

    BEGIN
        TEXT T;
        INTEGER I, M;
        FOR T :- "Su", "Mo", "Tu", "We", "Th", "Fr", "Sa" DO BEGIN
            WDAYS(I) :- T; I := I+1;
        END;
        I := 0;
        FOR T :- "January", "February", "March",
                 "April", "May", "June",
                 "July", "August", "September",
                 "October", "November", "December" DO BEGIN
            MONTHS(I) :- NEW MONTH(T); I := I+1;
        END;
        I := 0;
        FOR M := 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 DO BEGIN
            MONTHS(I).DAYS := M; I := I+1;
        END;
    END;

    BEGIN

        PROCEDURE SPACE(N); INTEGER N;
        BEGIN
            WHILE N > 0 DO BEGIN
                OUTCHAR(' '); N := N-1;
            END;
        END SPACE;

        PROCEDURE INIT_MONTHS;
        BEGIN
            INTEGER I;

            IF MOD(YEAR,4) = 0 AND MOD(YEAR,100) <> 0 OR MOD(YEAR,400) = 0 THEN
                MONTHS(1).DAYS := 29;

            YEAR := YEAR-1;
            MONTHS(0).START_WDAY
                := MOD(YEAR * 365 + YEAR//4 - YEAR//100 + YEAR//400 + 1, 7);

            FOR I := 1 STEP 1 UNTIL 12-1 DO
                MONTHS(I).START_WDAY :=
                    MOD(MONTHS(I-1).START_WDAY + MONTHS(I-1).DAYS, 7);

            COLS := (WIDTH + 2) // 22;
            WHILE MOD(12,COLS) <> 0 DO
                COLS := COLS-1;
            GAP := IF COLS - 1 <> 0 THEN (WIDTH - 20 * COLS) // (COLS - 1) ELSE 0;
            IF GAP > 4 THEN
                GAP := 4;
            LEAD := (WIDTH - (20 + GAP) * COLS + GAP + 1) // 2;
            YEAR := YEAR+1;
        END INIT_MONTHS;

        PROCEDURE PRINT_ROW(ROW); INTEGER ROW;
        BEGIN
            INTEGER C, I, FROM, UP_TO;
            INTEGER PROCEDURE PREINCREMENT(I); NAME I; INTEGER I;
            BEGIN I := I+1; PREINCREMENT := I;
            END PREINCREMENT;
            INTEGER PROCEDURE POSTINCREMENT(I); NAME I; INTEGER I;
            BEGIN POSTINCREMENT := I; I := I+1;
            END POSTINCREMENT;
            FROM := ROW * COLS;
            UP_TO := FROM + COLS;
            SPACE(LEAD);
            FOR C := FROM STEP 1 UNTIL UP_TO-1 DO BEGIN
                I := MONTHS(C).MNAME.LENGTH;
                SPACE((20 - I)//2);
                OUTTEXT(MONTHS(C).MNAME);
                SPACE(20 - I - (20 - I)//2 + (IF C = UP_TO - 1 THEN 0 ELSE GAP));
            END;
            OUTIMAGE;

            SPACE(LEAD);
            FOR C := FROM STEP 1 UNTIL UP_TO-1 DO BEGIN
                FOR I := 0 STEP 1 UNTIL 7-1 DO BEGIN
                    OUTTEXT(WDAYS(I)); OUTTEXT(IF I = 6 THEN "" ELSE " ");
                END;
                IF C < UP_TO - 1 THEN
                    SPACE(GAP)
                ELSE
                    OUTIMAGE;
            END;

            WHILE TRUE DO BEGIN
                FOR C := FROM STEP 1 UNTIL UP_TO-1 DO
                    IF MONTHS(C).AT_POS < MONTHS(C).DAYS THEN
                        GO TO IBREAK;
            IBREAK:
                IF C = UP_TO THEN
                    GO TO OBREAK;

                SPACE(LEAD);
                FOR C := FROM STEP 1 UNTIL UP_TO-1 DO BEGIN
                    FOR I := 0 STEP 1 UNTIL MONTHS(C).START_WDAY-1 DO
                        SPACE(3);
                    WHILE POSTINCREMENT(I) < 7 AND MONTHS(C).AT_POS < MONTHS(C).DAYS DO BEGIN
                        OUTINT(PREINCREMENT(MONTHS(C).AT_POS),2);
                        IF I < 7 OR C < UP_TO - 1 THEN
                            SPACE(1);
                    END;
                    WHILE POSTINCREMENT(I) <= 7 AND C < UP_TO-1 DO
                        SPACE(3);
                    IF C < UP_TO - 1 THEN
                        SPACE(GAP - 1);
                    MONTHS(C).START_WDAY := 0;
                END;
                OUTIMAGE;
            END;
        OBREAK:
            OUTIMAGE;
        END PRINT_ROW;

        PROCEDURE PRINT_YEAR;
        BEGIN
            INTEGER ROW;
            TEXT BUF;
            INTEGER STRLEN;
            BUF :- BLANKS(32); BUF.PUTINT(YEAR); BUF.SETPOS(1);
            WHILE BUF.MORE AND THEN BUF.GETCHAR = ' ' DO
                STRLEN := STRLEN+1;
            BUF :- BUF.SUB(STRLEN+1, 32-STRLEN);
            SPACE((WIDTH - BUF.LENGTH) // 2);
            OUTTEXT(BUF); OUTIMAGE; OUTIMAGE;
            WHILE ROW * COLS < 12 DO BEGIN
                PRINT_ROW(ROW);
                ROW := ROW+1;
            END;
        END PRINT_YEAR;

        INIT_MONTHS;
        PRINT_YEAR;
    END;
END;