CREATE TABLE table_26820 ("Rank" FLOAT, "Senator" TEXT, "Date of birth" TEXT, "Entered Senate" TEXT, "Left Senate" TEXT, "State served" TEXT, "Party" TEXT, "Time since entry" TEXT)

On what date did congressman joseph tydings enter take his seat?
SELECT "Entered Senate" FROM table_26820 WHERE "Senator" = 'Joseph Tydings'
SELECT "Entered Senate" FROM "table_26820" WHERE "Senator" = 'Joseph Tydings'