In fine diei pater dicit finem tandem venire.

Because in can take the ablative when it means in, on, at, during rather than motion into something.

Here in fine diei means at the end of the day, so fine is ablative singular of finis.

Compare:

• in urbe = in the city
• in fine diei = at the end of the day

If there were motion into something, Latin would more often use in + accusative.

Diei means of the day. It is the genitive singular of dies.

So in fine diei literally means in the end of the day, which is a normal Latin way to say at the end of the day.

This is a common pattern in Latin:

• initium belli = the beginning of the war
• finis viae = the end of the road
• finis diei = the end of the day

Yes. They both come from finis, which means end.

In this sentence they appear in two different cases because they do two different jobs:

• fine = ablative, after in in in fine diei
• finem = accusative, used as the subject of the infinitive in the indirect statement

So although they look different, they are just different forms of the same noun.

Because Latin uses the accusative + infinitive construction after verbs like dicit.

So in pater dicit finem tandem venire, the literal structure is:

• pater dicit = father says
• finem venire = the end to come

In normal English we would say father says that the end is finally coming.
Latin does not usually use a separate word for that here. Instead, it puts the subject of the reported idea into the accusative and uses an infinitive.

So finem is accusative because it is the subject of venire inside indirect statement.

Because after dicit, Latin often reports a statement with an indirect statement, also called accusative and infinitive.

So instead of saying the equivalent of father says that the end finally comes, Latin says:

• pater dicit finem tandem venire

Literally: father says the end finally to come

This is one of the most important sentence patterns in Latin.

Common examples:

• dico eum venire = I say that he is coming
• putat hostes adesse = he thinks that the enemies are near
• scimus hoc verum esse = we know that this is true

There is no separate word for that here.

In English, we usually say Father says that the end is coming.
In Latin, after a verb of saying, thinking, knowing, hearing, and so on, the language often uses accusative + infinitive instead of a that-clause.

So:

• English: he says that the end is coming
• Latin: dicit finem venire

The grammar itself shows the meaning, so Latin does not need a separate word for that.

Because pater is the main subject of the sentence.

It is the person doing the saying:

• pater = father
• dicit = says

So pater must be nominative singular.

The sentence has two layers:

1. Main clause: pater dicit
2. Reported statement: finem tandem venire

That is why pater is nominative, while finem is accusative.

Here tandem means something like finally, at last, or after all this time.

It often adds a sense of relief, impatience, or completion.

So finem tandem venire suggests:

• the end is finally coming
• the end is at last arriving

It is a small word, but it often carries emotion or emphasis.

Yes. It is perfectly normal Latin, even though it does not match English word order.

Latin word order is more flexible because the endings show the grammar. This lets Latin arrange words for emphasis or style.

Here:

• In fine diei sets the time first
• pater gives the subject
• dicit gives the main verb
• finem tandem venire gives the reported statement

A very literal order is:

• At the end of the day father says the end finally to come

That sounds odd in English, but it is natural enough in Latin.

Usually in fine diei is best understood as at the end of the day.

By the end of the day often suggests a deadline in English, and Latin would more likely use some other expression if that were the main idea.

So here the phrase is probably a time setting:

• at day’s end
• at the end of the day

Latin often uses verbs of motion in ways that sound very natural in English too.

Venire means to come, so finem venire means the end is coming or more literally the end comes.

English does the same thing:

• winter is coming
• the time has come
• the end is coming

So this is not a strange Latin expression at all.

Dies is usually masculine, especially in the singular, and that is the usual assumption here.

So diei is the genitive singular of a fifth-declension noun that is generally masculine:

• nominative: dies
• genitive: diei

You may sometimes see dies treated as feminine in certain contexts, especially when it means an appointed day or date, but that is not the main issue in this sentence.

Yes, and that is a helpful way to notice the structure.

The first end is part of a time phrase:

• in fine diei = at the end of the day

The second end is the thing being talked about:

• finem tandem venire = the end is finally coming

So Latin repeats the noun finis in two different roles:

• one end belongs to the day
• the other end is the subject of the reported statement

That repetition may sound dramatic or pointed, and Latin often allows that kind of effect.