I already posted info about the trip of Hermann Buhl. My source is the biography by Horst Höfler, AS Verlag, Zuerich 2003, where the original trip report of Buhl is printed. And there Buhl wrote that he started on February 28th at 7 pm at St. Bartholomae.
Thank you for the correction that Buhl wasn't the first in winter in the east face.
First successful winter-mountaineers were Toni Beringer, Simon Flatscher, Ludwig Zankl (all Bad Reichenhall) and Georg Mitterer (Trostberg). Date was 6th to 8th of December 1930.
Salzburger Weg (Route Salzburg):
First climb through "Salzburger Weg" in winter by Bernulf Freiherr von Crailsheim, Thomas Freiberger, Konrad Hollerieth, 8th to 10th of January 1949.
Hermann Buhl from Innsbruck ascended the route called "Salzburger Weg" (UIAA IV+ / A0) solo and in the winter night(!) from 27 th to 28th of February in 1953. It was a training for his first ascend of Nanga Parbat in the Summer of the same year. He didn't know this route from summer.
Münchener Weg (Munich route):
First ascend of "Münchener Weg" in winter: Karl and Fritz Krämer (Frankfurt), Oskar Dorfmann (Regensburg), 28th of March to 1st of April 1949
Berchtesgadener Weg (Berchtesgaden route):
First winter climb: 29th to 31st of March 1949 by Werner Kohn, Reinhard Sander (both Frankfurt).
Source: Hellmut Schöner: Zweitausend Meter Fels. Ein Watzmann-Ostwand-Buch.
7th edition 1981.