Mayor Thomas M. Menino will not attend the inauguration of his successor, Martin J. Walsh, on Jan. 6. Dot Joyce, Menino's spokeswoman, said he had already made plans to go on vacation by the time inaugural details were finalized. She said Menino believes the inauguration is "Marty Walsh's day," and the mayor will meet with him that morning to hand over the reins. Joyce said Menino does not wish to slight Walsh, but rather wants to honor the fact that he will be the new mayor. Menino's decision was first reported by the Boston Herald.