CREATE TABLE table_12615 ("Year" FLOAT, "Award Ceremony" TEXT, "Category" TEXT, "Nominee" TEXT, "Result" TEXT)

Which Year has a Category of best performance by a leading actress in a musical?
SELECT MAX("Year") FROM table_12615 WHERE "Category" = 'best performance by a leading actress in a musical'
SELECT MAX("Year") FROM "table_12615" WHERE "Category" = 'best performance by a leading actress in a musical'