" Originally,” Langdon said, “Christianity honored the Jewish Sabbath of Saturday, but Constantine shifted it to coincide with the pagan’s veneration day of the sun.” He paused, grinning. “To this day, most churchgoers attend services on Sunday morning with no idea that they are there on account of the pagan sun god’s weekly tribute—Sunday. "

― Dan Brown , The Da Vinci Code (Robert Langdon, #2)