Hayom Yom (Hebrew: היום יום‎, "Today is day ...") is a calendar for the Hebrew year of 5703 (1942-3), compiled by Rabbi Menachem Mendel Schneerson at the behest of his father-in-law, Rabbi Yosef Yitzchok Schneersohn, in the winter of 1942.For each day, the calendar prescribed sections of Chumash, Tehillim, and Tanya for study that day; this practice is known in Chabad-Lubavitch as Chitas (חת"ת).