The Rebbe blesses Rabbi Yosef Chaim Shlomo on his granddaughter’s wedding and shares that he’s unaware of a source from the Tzemach Tzedek about wearing a watch on Shabbos. He explains that Shabbos can influence earlier days, as its holiness begins before its actual onset.
https://www.torahrecordings.com/rebbe/004_igros_kodesh/nissan/978