[288]. 1. Cum, when referring to the past, takes,—
A. The Indicative (Imperfect, Historical Perfect, or Pluperfect) to denote the point of time at which something occurs.
B. The Subjunctive (Imperfect or Pluperfect) to denote the situation or circumstances under which something occurs.
Examples:—
INDICATIVE.
an tum erās cōnsul, cum in Palātiō mea domus ārdēbat, or were you consul at the time when my house burned up on the Palatine?
crēdō tum cum Sicilia flōrēbat opibus et cōpiīs magna artificia fuisse in eā īnsulā, I believe that at the time when Sicily was powerful in riches and resources there were great crafts in that island;
eō tempore pāruit cum pārēre necesse erat, he obeyed at the time when it was necessary to obey;
illō diē, cum est lāta lēx dē mē, on that day when the law concerning me was passed.
SUBJUNCTIVE.
Lysander cum vellet Lycūrgī lēgēs commūtāre, prohibitus est, when Lysander desired to change the laws of Lycurgus, he was prevented;
Pythagorās cum in geōmetriā quiddam novī invēnisset, Mūsīs bovem immolāsse dīcitur, when Pythagoras had discovered something new in geometry, he is said to have sacrificed an ox to the Muses.
a. Note that the Indicative is much less frequent in such clauses than the Subjunctive, and is regularly confined to those cases where the main clause has tum, eō diē, eō annō, eō tempore or some similar correlative of the cum. Sometimes it depends entirely upon the point of view of the writer whether he shall employ the Indicative or Subjunctive.
2. Cum Inversum. When the logical order of the clauses is inverted, we find cum with the Perfect Indicative or Historical Present, in the sense of when, when suddenly. The main clause in such cases often has jam, vix, aegrē, nōndum; as,—