13 January 1942:
“. . .The first ejection seats were developed independently during World War II by Heinkel and SAAB. Early models were powered by compressed air and the first aircraft to be fitted with such a system was the Heinkel He 280 prototype jet-engined fighter in 1940. One of the He 280 test pilots, Helmut Schenk, became the first person to escape from a stricken aircraft with an ejection seat on 13 January 1942 after his control surfaces iced up and became inoperable. The fighter, being used in tests of the Argus As 014 impulse jets for Fieseler Fi 103 missile development, had its usual HeS 8A turbojets removed, and was towed aloft from Rechlin, Germany by a pair of Bf 110C tugs in a heavy snow-shower. At 7,875 feet (2,400 m), Schenk found he had no control, jettisoned his towline, and ejected. . . .”
—Wikipedia
German Wikipedia on the 280 says 13. January 1943, not 1942; the german wp-article about Rechlin test range also.
This sounds plausible, since the first Argus AS 109-014 weren´t delivered until late 1942.
First (test-) ejection btw with an ejection-seat in germany was early 1941, by Wilhelm Buss, also at Rechlin test range.
This is why I don’t like to use Wikipedia as a source.