Nor is POPE. Or SINLESS MARY. Or RESURRECTED MARY. Or a SAINT’S PRAYER LINE IN HEAVEN.
What’s your point? Beside SEEMING to show ignorance again?
We all celebrate Christmas on December 25th even though that date isn't in the Bible; the Catholic Church teaches us that this the day that the Messiah was born.
We don't celebrate Easter the day after Passover (which is when the Bible tells us the first Easter Sunday was); we celebrate it on the first Sunday that follows the first full moon after the vernal equinox, because this is the day the Catholic Church declares Easter Sunday to be.
We don't take our day of rest on the Jewish Sabbath (which was the day of rest in the Bible); we take it on Sunday, because the Catholic Church has moved it to Sunday (and declared it so at the Council of Laodicea in 360).
(If you're taking your day of rest on Sunday, you're doing this without any biblical basis. In fact, you're following a Catholic practice of using either Sacred Tradition as your source.)