>select table1.*, space(x) as BBal from table1 ;
> union select table2.*, space(x) as ABal from table2 ;
> into cursor c_result
>

Actually, unless an instance of a value for Date only appeared in either Table1 or in Table2, never in both, you need a Full Outer Join, followed by a reduction to merge the two dates (one of which might otherwise be null)

SELECT Table1.Date AS DateA, ABal, Table2.Date AS DateB, BBal ;
   FROM Table1 ;
   FULL OUTER JOIN Table2 ON Table1.Date = Table2.Date ;
   INTO CURSOR (SYS(2015))
lcAlias = ALIAS()
SELECT IIF(ISNULL(DateA), DateB, DateA) AS Date, ABal, BBal ;
   FROM (lcAlias) ;
   INTO CURSOR c_result
USE IN (lcAlias)

You could have the option of using IIF(ISNULL()) or NVL() constructs to strip nulls from ABal and BBal in c_result if you couldn't deal with nulls or wanted to see specific values where nulls were found.