you could decompose the string and recompose in a date-like format, the cast and convert both work ok in sql query. dunno about informatica. the date string you provided was 19820101, not sure if it's yyyymmdd or yyyyddmm, you'll have to move the substring around if it's the latter.
select
ISDATE(SUBSTRING(@Bday,1,4) + '-' + SUBSTRING(@Bday,5,2) + '-' + SUBSTRING(@Bday,7,2))
, SUBSTRING(@Bday,1,4) + '-' + SUBSTRING(@Bday,5,2) + '-' + SUBSTRING(@Bday,7,2)
,CAST (SUBSTRING(@Bday,1,4) + '-' + SUBSTRING(@Bday,5,2) + '-' + SUBSTRING(@Bday,7,2) AS DATE)
,CONVERT(DATE , SUBSTRING(@Bday,1,4) + '-' + SUBSTRING(@Bday,5,2) + '-' + SUBSTRING(@Bday,7,2))
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