LU: What I meant was that the Chazon Ish paskened was to treat one day as completely weekday and the other as Yom Kippur. I will try to explain this and hope it is correct. There are 24 time zones across the globe based on the 24 longitudes. According to the accepted International Date Line it is currently Tuesday 5:30 PM in NY, Wednesday 12:30 AM in EY and Wednesday 7:30 AM in Japan. What we say is that Japan is 7 hours ahead of EY time. However, according to the Chazon Ish, the Halachic Date Line is 90 degrees East of EY. Japan is 100 degrees East of EY. Therefore, halachically Japan is 17 hours BEHIND EY time and it is actually 7:30 AM TUESDAY. If I remember correctly, Yom Kippur in 1941 was on a Thursday. Therefore, when it was Thursday in EY it was halachically still Wednesday in Japan even though by the accepted dateline it was called Thursday. When Yom Kippur started in EY, it was still weekday in Japan and Yom Kippur wouldn’t start for another 17 hours. On that day, the Mirrer Mashgiach, R’ Chatzkel Levenshtein came to shacharis with his tallis and tefillin and treated the day as a weekday and they held Yom Kippur on the following day.
My source for this is the biography of the Chazon Ish, printed by Mesorah Publications (ArtScroll).