When did Mathias Rust illegally land at the Red Square in the capital of the Soviet Union?

Mathias Rust, aged 18, was an inexperienced pilot, with about 50 hours of flying experience at the time of his flight. On May 13, 1987, he left Uetersen near Hamburg in his rented Reims Cessna F172P D-ECJB. On May 28, 1987, Rust crossed the Baltic coastline over Estonia and turned towards Moscow. At 14:29 he appeared on the Soviet Air Defence Forces radars. After his failure to reply to the ID signal three battalions of 54th Air Defence Corps tracked him for some time but failed to obtain permission to launch at him. Then he disappeared from the radar. Around 7:00 p.m. Rust appeared above Moscow. He had initially intended to land in the Kremlin, but he reasoned that landing inside, hidden by the Kremlin walls, would have allowed the KGB to arrest him and deny the incident. Therefore, he changed his landing spot. He landed on Vasilevsky Descent next to St. Basil's Cathedral at the Red Square.

He was greeted by curious passersby and was asked for autographs. Two hours later he was arrested.

In September 1987 Mathias Rust was sentenced to four years in a general-regime labor camp for hooliganism, for disregard of aviation laws, and for breaching the Soviet border. He was never transferred to a labor camp but was kept in a prison in Moscow. Two months later, Reagan and Gorbachev agreed to sign a treaty to eliminate intermediate-range nuclear weapons in Europe, and the Supreme Soviet ordered Rust to be released in August 1988 as a goodwill gesture to the West.