Error "One of the identified items was in an invalid format" was received.
Workbench can only process dates within a valid .Net DateTime type range of values, that is from 00:00:00.0000000 UTC, January 1, 0001 to 23:59:59.9999999 UTC, December 31, 9999. You will see this error if you have data values outside this range like dates containing BC.
Use cast to convert the dates into strings. For example "select my_date::varchar(30) from <table name>"
Workbench for Redshift (all versions)