CREATE TABLE table_71381 ("Polling Firm" TEXT, "Date" TEXT, "Link" TEXT, "PSOE" TEXT, "Others" TEXT, "Lead" TEXT)

Which date has a PSOE of 36.1%?
SELECT "Date" FROM table_71381 WHERE "PSOE" = '36.1%'
SELECT "Date" FROM "table_71381" WHERE "PSOE" = '36.1%'