CREATE TABLE table_16513 ("Team" TEXT, "Outgoing manager" TEXT, "Manner of departure" TEXT, "Date of vacancy" TEXT, "Replaced by" TEXT, "Date of appointment" TEXT)

What days is greenock morton vacant?
SELECT "Date of vacancy" FROM table_16513 WHERE "Team" = 'Greenock Morton'
SELECT "Date of vacancy" FROM "table_16513" WHERE "Team" = 'Greenock Morton'