“It was evening and it was morning, the sixth day, [and heaven and earth were finished…]” (Genesis 1:31–2:1) – Rabbi Yudan said: This is the additional hour [late Friday afternoon] that one takes away from the profane and adds to the sacred [Shabbat], during which the labor of the world was completed.23God finished the process of creation before the very end of the sixth day, so the end of Friday is itself appended to Shabbat.
That is why “the sixth [day, and heaven and earth were finished]” is written. Rabbi Simon ben Marta said: Until this point, one reckons [the days] according to the count of the world,24The first day of creation, the second day of creation, etc. from here on, one reckons according to a different count.25After this point, one does not count the number of days since creation, but the number of days after Shabbat: The first day after Shabbat (Sunday), the second day after Shabbat (Monday), etc.