CREATE TABLE table_22957 ("Team" TEXT, "Outgoing manager" TEXT, "Manner of departure" TEXT, "Date of vacancy" TEXT, "Replaced by" TEXT, "Date of appointment" TEXT, "Position in table" TEXT)

When did the old manager vacate his position in Plymouth Argyle?
SELECT "Date of vacancy" FROM table_22957 WHERE "Team" = 'Plymouth Argyle'
SELECT "Date of vacancy" FROM "table_22957" WHERE "Team" = 'Plymouth Argyle'