The phrase "the day" is an idiom that refers to a specific event happening. Alternate translation: "You have done what you have promised" (See: [[rc://en/ta/man/translate/figs-idiom]])
This is a request for Jerusalem's enemies to suffer as the people of Jerusalem have. Alternate translation: "now let them suffer like me" (See: [[rc://en/ta/man/translate/figs-explicit]])