SELECT "Date" FROM table_70231 WHERE "Year" > '1978' AND "Location" = 'memorial stadium (baltimore)'
What is the Date, when the Year is after 1978, and when the Location is Memorial Stadium (Baltimore)?
CREATE TABLE table_70231 (
    "Year" real,
    "Date" text,
    "Winner" text,
    "Result" text,
    "Loser" text,
    "Location" text
)