The antonyms of "ante-dated" include "postdate," "modernize," "update," and "contemporize." When something is ante-dated, it means that it is assigned a date earlier than the current date. Its antonyms, on the other hand, mean giving a later date or bringing something up to date with current trends and standards. For example, when a document is postdated, it means that the date on it is a later date compared to the actual date it was created. Modernizing or updating something means making it more current or relevant to the present time. Contemporizing something refers to making it fashionable or trendy by adapting it to current styles and trends.