CREATE TABLE table_4142 ("By-election" FLOAT, "Electorate" CLOB, "Date" CLOB, "Incumbent" CLOB, "Reason" CLOB, "Winner" CLOB)

When ihaia tainui is the incumbent what is the date?
SELECT "Date" FROM table_4142 WHERE "Incumbent" = 'Ihaia Tainui'
SELECT "Date" FROM "table_4142" WHERE "Incumbent" = 'Ihaia Tainui'