Airport runway numbers are based off their magnetic headings with the last zero removed. So a runway that runs due south/north is 18/36 (i.e., it faces 180 degrees south and 360 degrees north - 0 isn't used). A runway that runs due east/west is 9/27. And so on. When there are parallel runways facing the same direction, the L, C, and R designations are used. A pair for parallel east/west runways are 9R/27L and 9L/27R.
So as the pole drifts this sometimes causes runways to have be renumbered. One previous example is Reagan-National airport in Washington, D.C., where runways 1/19 and 4/22 were originally 18/36 and 3/21.
Well, okay, that last statement isn't entirely true.