Can I post couplets on the nineteenth day of the first month?

You can't. The role of Spring Festival couplets is to ward off evil spirits and look forward to a good year in the coming year, so no matter where they are posted, the time should not exceed New Year's Eve at the latest. Couplets, one of the traditional cultures in China, also called couplets or couplets, are antithetical sentences written on paper, cloth or engraved on bamboo, wood and columns.