CREATE TABLE table_45100 ("Date" TEXT, "Tournament" TEXT, "Winning score" TEXT, "Margin of victory" TEXT, "Runner ( s ) -up" TEXT)

What is Date, when Tournament, is Greenbrier Classic?
SELECT "Date" FROM table_45100 WHERE "Tournament" = 'greenbrier classic'
SELECT "Date" FROM "table_45100" WHERE "Tournament" = 'greenbrier classic'