Oracle 18c

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create table t1 (dt) as  
    select date'2020-01-01'+(level-1) 
    from dual connect by level<=(date'2020-06-24'-date'2020-01-01'+1)
176 rows affected

create table t2 (dt) as  
    select date'2020-05-01'+(level-1) 
    from dual connect by level<=(date'2020-05-31'-date'2020-05-01'+1)
31 rows affected

select 
    min (l.dt)||'-'||max (l.dt) lower, 
    min (u.dt)||'-'||max (u.dt) upper
from t1 l cross join t1 u 
cross join (select min (dt) lb, max (dt) ub from t2) 
where l.dt < lb
and   u.dt > ub


LOWER
UPPER


01-JAN-20-30-APR-20
01-JUN-20-24-JUN-20