Qs have been asked about expressions-of-time, of the type: "in the second year" = "secondo anno"; "within three days" = "tribus diebus"; "for two years" = "(per) duos annos" ("per" is optional) which follow logical patterns of case-endings. Some are not so clear-cut.
North & Hillard Ex. 200: the following is to be translated into Latin:
He was not the man to put his own prosperity before that of the state; and he used to say that when his countrymen needed him they would recall him; till that time should arrive he was willing to remain in exile.
Translation: non enim is fuit qui suum commodum republicae anteponeret et affirmabat cives suos se cum opus esset, revocaturos; quod ad tempus (ad id temporis) se velle in exsilio manere.
N & H have offered two expressions-of-time: firstly, "ad tempus" usually given as "on time" (ad + accusative) lit. "to-the-time (appointed)" ("on time" can be given as dative, "tempori", which translates sensibly to "to/ for-the-time"; but, may lead to confusion as to which one to use--does it matter?). Here "ad tempus" clearly means "temporarily"; "temporarily, he was content to remain in exile". In the dict. listings "ad + acc." can mean "for": "ad tempus" = "for-the-time (being)" = "temporarily".
Secondly, alternative "ad id temporis". In "General Vocabulary", p.297, N & H give this as "till that time"; but, lit. "to that (presumably "event") of-the-time" (using the genitive), without adding a lot of extra words e.g. "that-it (the event)-may-happen" it makes little sense, in English. How does "ad id temporis" come to mean "till that time", in Latin? This does, of course, fit the translation "till that time, of his recall, he was content to remain in exile".
Continuing with Titus Livius (Livy XL. 4):
ad multo ante praecogitatum revoluta facinus…
translation: having fallen back to a purpose that she imagined long before...
Pock. Ox. Lat. Dict. gives adverb "multo" = "long (before or after)"; therefore not requiring "ante"; alternatively, using "ante" as adverb, putting the period of time into the ablative, giving Livy's "multo ante"; but this particular type of expression is usually more clearly defined e.g. "duobus ante annis" = "two years before" (adverb must be written after at least one of the relevant words in the ablative). Nevertheless, am guessing that, here (Livy), this is ablative "multo" + "ante", is this correct?