20 wickets, 2 declarations happened on same day of a Test
On day three of the Brisbane Ashes Test played on December 4, 1950, 20 wickets fell and two innings were declared. Trailing by 160 runs, England declared their first innings to make Australia bat on the unplayable pitch. Australia declared their second innings after being reduced to 32-7, following which England lost the match after finishing the day on 30-6.