On the night of December 25, 1991, at 7:32 p.m. Moscow time, after Gorbachev left the Kremlin, the Soviet flag was lowered for the last time, and the Russian tricolor was raised in its place, symbolically marking the end of the Soviet Union. The next day, December 26, 1991, the Council of Republics, the upper chamber of the Union's Supreme Soviet, issued a formal Declaration recognizing that the Soviet Union had ceased to exist as a state and subject of international law, and voted both itself and the Soviet Union out of existence (the other chamber of the Supreme Soviet, the Council of the Union, had been unable to work since December 12, 1991, when the recall of the Russian deputies left it without a quorum). The following day Yeltsin moved into Gorbachev's former office, though the Russian authorities had taken over the suite two days earlier. By December 31, 1991, the few remaining Soviet institutions that had not been taken over by Russia ceased operation, and individual republics assumed the central government's role.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): When did Gorbachev make his final Kremlin exit?
December 25, 1991, at 7:32 p.m. Moscow time