When Reb Yoel Kahn discovered that his Shabbos guest had crossed the International Date Line during sefiras ha’omer, he realized that for him, Shabbos was already the fiftieth day of the Omer, and the yomtov of Shavuos. Uncertain of what his guest should do, he advised him to approach the Rebbe directly as he left the shul after shachris.