WITH
cte AS( SELECT
            COALESCE(LAG(start_date) OVER(ORDER BY start_date), '1900-01-01') AS prev_date,
            start_date, end_date,
            COALESCE(LEAD(end_date) OVER(ORDER BY end_date), '2100-01-01') AS next_date
        FROM projects),
        
cte2 AS ( SELECT start_date, ROW_NUMBER() OVER(ORDER BY start_date) AS rn
        FROM cte 
        WHERE ABS(DATEDIFF(DAY, start_date, prev_date)) <> 1),
        
cte3 AS ( SELECT end_date , ROW_NUMBER() OVER(ORDER BY end_date) AS rn
        FROM cte 
        WHERE ABS(DATEDIFF(DAY, next_date, end_date)) <> 1)

SELECT cte2.start_date, cte3.end_date
FROM cte2
JOIN cte3 ON cte2.rn = cte3.rn
ORDER BY ABS(DATEDIFF(DAY, cte2.start_date, cte3.end_date)), cte2.start_date;