Monthly calendar

S

Simple calendar for whole year usable month by month.

SELECT
    TO_NUMBER(SUBSTR(x.week, 3))                                                AS week,
    x.month,
    MAX(DECODE(TO_CHAR(x.day, 'D'), '1', TO_NUMBER(TO_CHAR(x.day, 'FMDD'))))    AS mon,
    MAX(DECODE(TO_CHAR(x.day, 'D'), '2', TO_NUMBER(TO_CHAR(x.day, 'FMDD'))))    AS tue,
    MAX(DECODE(TO_CHAR(x.day, 'D'), '3', TO_NUMBER(TO_CHAR(x.day, 'FMDD'))))    AS wed,
    MAX(DECODE(TO_CHAR(x.day, 'D'), '4', TO_NUMBER(TO_CHAR(x.day, 'FMDD'))))    AS thu,
    MAX(DECODE(TO_CHAR(x.day, 'D'), '5', TO_NUMBER(TO_CHAR(x.day, 'FMDD'))))    AS fri,
    MAX(DECODE(TO_CHAR(x.day, 'D'), '6', TO_NUMBER(TO_CHAR(x.day, 'FMDD'))))    AS sat,
    MAX(DECODE(TO_CHAR(x.day, 'D'), '7', TO_NUMBER(TO_CHAR(x.day, 'FMDD'))))    AS sun
FROM (
    SELECT
        TRUNC(SYSDATE, 'Y') + LEVEL - 1                                         AS day,
        TO_CHAR(TRUNC(SYSDATE, 'Y') + LEVEL - 1, 'IYIW')                        AS week,
        TO_CHAR(TRUNC(SYSDATE, 'Y') + LEVEL - 1, 'MM/YYYY')                     AS month
    FROM DUAL
    CONNECT BY LEVEL <= ADD_MONTHS(TRUNC(SYSDATE, 'Y'), 12) - TRUNC(SYSDATE, 'Y')
) x
GROUP BY x.month, x.week
ORDER BY x.month, x.week;

You can calculate next day and also next business day (if you apply function above):

DECLARE
    in_date   CONSTANT DATE := TRUNC(SYSDATE);
    --
    FUNCTION next_date (
        in_day    CHAR,
        in_date   DATE := TRUNC(SYSDATE)
    )
    RETURN DATE AS
    BEGIN
        RETURN CASE in_day
            WHEN 'D' THEN
                in_date + 1
            WHEN 'W' THEN
                NEXT_DAY(in_date, TO_CHAR(TRUNC(in_date, 'D'), 'DY'))
            WHEN 'M' THEN
                LAST_DAY(in_date) + 1
            WHEN 'Q' THEN
                CASE WHEN EXTRACT(MONTH FROM in_date) MOD 3 = 0 THEN
                    TRUNC(ADD_MONTHS(in_date, 1), 'MM')
                ELSE
                    TRUNC(ADD_MONTHS(in_date, (3 - (EXTRACT(MONTH FROM in_date) MOD 3)) + 1), 'MM')
                END
            WHEN 'Y' THEN
                TO_DATE((EXTRACT(YEAR FROM in_date) + 1) || '-01-01', 'YYYY-MM-DD')
            END;
    END;
BEGIN
    -- show next day, week (Monday), quarter, year and number of days left
    FOR c IN (
        SELECT 'D' AS day_ FROM DUAL UNION ALL
        SELECT 'W' FROM DUAL UNION ALL
        SELECT 'M' FROM DUAL UNION ALL
        SELECT 'Q' FROM DUAL UNION ALL
        SELECT 'Y' FROM DUAL
    ) LOOP
        DBMS_OUTPUT.PUT_LINE(c.day_ || ' ' || TO_CHAR(next_date(c.day_, in_date), 'YYYY-MM-DD') || ' ' || LPAD(next_date(c.day_, in_date) - TRUNC(SYSDATE), 4));
    END LOOP;
END;
/

On a related note, you can set default NLS parameters for your session.

BEGIN
    DBMS_SESSION.SET_NLS('NLS_LANGUAGE',            '''CZECH''');
    DBMS_SESSION.SET_NLS('NLS_TERRITORY',           '''CZECH REPUBLIC''');
    DBMS_SESSION.SET_NLS('NLS_DATE_FORMAT',         '''DD.MM.RR''');
    DBMS_SESSION.SET_NLS('NLS_TIME_FORMAT',         '''HH24:MI:SSXFF''');
    DBMS_SESSION.SET_NLS('NLS_TIMESTAMP_FORMAT',    '''DD.MM.RR HH24:MI:SSXFF''');
END;
/