DECLARE @t TABLE (
    [Date] date
)

INSERT @t VALUES('2/29/2020')

;WITH year([date]) AS (
    SELECT CAST('1/1/2020' AS date)
    UNION ALL
    SELECT DATEADD(d, 1, [date])
        FROM year WHERE [date] < '12/31/2020'
)
SELECT * FROM year y 
    WHERE NOT EXISTS (
        select * from @t t where t.[Date] = y.[date] 
    ) 
OPTION (MAXRECURSION 0)

DECLARE @reserved_intervals TABLE (
    [from] date,
    [to] date
)

INSERT @reserved_intervals ([from], [to])
  VALUES('2/29/2020', '3/8/2020')

;WITH
year_days([date]) AS (
    SELECT CAST('1/1/2020' AS date)
    UNION ALL
    SELECT DATEADD(d, 1, [date])
        FROM year_days WHERE [date] < '12/31/2020'
),
reserved_days([date]) AS (
  SELECT [date] FROM year_days
    WHERE EXISTS(SELECT * FROM @reserved_intervals
        WHERE [date] BETWEEN [from] AND [to])
      
)
SELECT * FROM year_days y 
    WHERE NOT EXISTS (
        SELECT * FROM reserved_days rd WHERE rd.[date] = y.[date] 
    ) 
OPTION (MAXRECURSION 0)