The "steal a mirror" quote, to which Leon refers, derives from Kurt Vonnegut's book "Breakfast of Champions". To quote the book, Vonnegut's fictional science fiction writer, Kilgore Trout, "did another thing which some people might have considered eccentric: he called mirrors leaks. It amused him to pretend that mirrors were holes between two universes." Hence, "steal a mirror" could be restated as "take a leak".
The entire episode takes place entirely on December 26, 2015.