As is the case with most wizards in the Harry Potter series, his wand is among his most valued magical items. Harry's is made of holly, a wood Rowling chose because it is said to get rid of evil. It forms a deliberate contrast to the wand of his nemesis Lord Voldemort, whose wand is made of yew, which symbolises death. Rowling states she later learned that in the Celtic calendar a type of wood is assigned to each month; and Harry's fictional birthday (31 July) is linked to holly. Ron Weasley and Hermione Granger also happened to get wands made from the appropriate woods identified the Celtic calendar, according to their fictional birth months.