https://www.youtube.com/watch?v=F_pOY9MqRZg
Note: not from the same Latin Tutorial videos that have been referred to before; this one looks only at the two ablative usages discussed here.
[i] the ablative of time when: when referring to a specific point or period in time e.g. a clock time, a season, a year, the ablative without a preposition is used:
horā quartā │ at the fourth hour
prīmā lūce │ at dawn
nocte │ at night
hieme │ in winter
annō secundō │ in the second year
eōdem diē │ on the same day
[ii] as the term would suggest, the ablative of time within which indicates the period during which an action take place
tribus proximīs annīs │ within the next three years
paucīs hōrīs │ within a few hours
Diēbus vīgintī quīnque aggerem exstrūxērunt. (Caesar) │ Within twenty-five days they finished building a mound.
Cēnābis bene, mī Fabulle, apud mē │ You will dine well, my Fabullus, at my house
paucīs, sī tibi dī favent, diēbus, │ in a few days, if the gods favour you
Gaius Valerius Catullus
Image #4: expressions of time can be sub-divided into:
[1] Time when: refers to a specific point in time e.g. They set sail on the same day (eōdem diē).
[2] Time within which: the period of time taken to complete an action e.g. They will have reached the island within three days (tribus diēbus).
[1] and [2] have been discussed above. Both use the ablative case.
[3] Duration of time: for how long an action takes place; this is expressed in Latin by the accusative case:
Graecī Troiam multōs annōs oppugnāvērunt. │ The Greeks attacked Troy for many years.
Compare:
Quīnque hōrīs [ablative of time within which] ad urbem vēnērunt. │ They came to the city within five hours.
Quattuor annōs [accusative of duration] in illā urbe labōrāvit. │ He worked in that city for five years.
