Learn Hardcore Portuguese (Portugal): Um dia, hás de reler esse diário e ele há de lembrar‑te de quanto já aprendeste. - One day, you will reread that diary and it will remind you how much you have already learned.

hás de reler ≈ “you will (one day / eventually) reread”.
It often carries a nuance of inevitability, expectation or strong belief: “you’re bound to reread it”, “you surely will reread it (someday)”.

Other options:

relerás esse diário – simple future; grammatically fine but sounds more formal/literary in modern spoken European Portuguese.
vais reler esse diário – ir + infinitive, the most common neutral spoken future.
hás de reler esse diário – a bit more expressive, slightly literary, fits very well with Um dia (“one day”).

So hás de is not wrong or archaic; it just adds that “one day / eventually, I’m sure this will happen” flavour.

Why is it hás de reler and not há de reler?

Because hás is the 2nd person singular (tu) form of haver, while há is 3rd person singular (ele/ela/você).

(tu) hás de reler – you (informal, singular) will reread
(ele/ela/você) há de reler – he/she/you (formal) will reread

In the sentence:

Um dia, hás de reler esse diário… → the subject is tu (you, informal).
…e ele há de lembrar‑te… → the subject here is ele (it / he = the diary).

So the forms agree with different subjects in each clause:

tu hás de reler
ele há de lembrar‑te

Is hás de formal or old‑fashioned in European Portuguese?

It’s not exactly old‑fashioned, but it is:

more common in written language (books, thoughtful speech, storytelling).
less common in very casual everyday talk, where vais + infinitive is more usual.

Nuance in EP:

Hei de / hás de / há de… – still heard, especially to sound a bit more expressive or emphatic: “Um dia hás de perceber…”
In relaxed speech the same idea is often “Um dia vais perceber…”.

So your sentence feels natural, a bit literary / reflective, not stiffly formal.

Why is there a comma after Um dia?

Um dia is a sentence‑initial time expression (an adverbial phrase). In European Portuguese:

It’s very common and stylistically preferred to separate this kind of fronted element with a comma:
- Um dia, hás de reler esse diário…
The comma visually marks a pause and separates the time setting from the main clause.

In informal texts you could see it without the comma, but with the comma is the standard and clearer choice.

What does ele refer to in e ele há de lembrar‑te? Could we omit ele?

Ele refers back to esse diário:

esse diário → masculine singular → ele (“it” in English).

So:

…hás de reler esse diário e ele há de lembrar‑te…
= “…you will reread that diary and it will remind you…”

Can you omit ele?

*… e há de lembrar‑te… is grammatical, but it’s less clear, because:
- The previous subject was tu (implied in hás de reler).
- If you drop ele, it’s not immediately obvious that the subject has changed to the diary.

Portuguese is a pro‑drop language, so subject pronouns can be omitted when the subject is clear. Here, ele is kept to signal the change of subject and avoid confusion.

Why is the pronoun written as lembrar‑te and not te lembrar?

In European Portuguese, unstressed object pronouns (like te) usually attach to the verb with a hyphen in affirmative clauses when nothing attracts them to the front. This is called enclisis.

Here the main content verb is lembrar in the infinitive:

lembrar + te → lembrar‑te

With haver de + infinitive, the pronoun normally attaches to the infinitive, not to há:

ele há de lembrar‑te (most natural in EP)
ele vai lembrar‑te (with ir + infinitive, same pattern)

Forms like ele te há de lembrar are more unusual and sound bookish/archaic.
In Brazilian Portuguese, people much more often say ele vai te lembrar, with the pronoun before the infinitive.

What is the difference between lembrar‑te de and lembrar‑te? Why is de needed?

The verb lembrar has two main patterns:

lembrar alguém de algo – to remind someone of something
- Ele há de lembrar‑te de quanto já aprendeste.
  → It will remind you of how much you’ve already learned.
- Structure: lembrar + [alguém] + de + [conteúdo]
lembrar‑se de algo – to remember something (reflexive)
- Lembras‑te de mim? – Do you remember me?

In your sentence we are in pattern (1), “remind someone of something”, so we need de before the clause expressing what it reminds you of:

lembrar‑te de quanto já aprendeste
= remind you of how much you’ve already learned

Without de (*lembrar‑te quanto já aprendeste) it sounds incorrect or at least non‑standard in European Portuguese.

What does quanto mean in de quanto já aprendeste?

Here quanto means “how much” (not “how many”):

de quanto já aprendeste = “of how much you’ve already learned”.

Grammatically:

quanto is a relative / exclamative pronoun introducing a clause:
- quanto já aprendeste = “how much you’ve already learned”.
With de, it becomes the complement of lembrar‑te de:
- lembrar‑te de quanto já aprendeste.

Close alternatives with slightly different style:

de como já aprendeste tanto – “of how you’ve already learned so much”
do muito que já aprendeste – “of how much you’ve already learned” (literally “of the much that you’ve already learned”)

Why is it já aprendeste and not something like tens aprendido (present perfect) or tinhas aprendido (past perfect)?

Já aprendeste is the pretérito perfeito simples (simple past, 2nd person singular):

(tu) aprendeste = “you learned / you have learned”.

In European Portuguese:

pretérito perfeito (aprendeste) often covers what English expresses with the present perfect:
- quanto já aprendeste ≈ “how much you have already learned”.

The form tens aprendido in EP usually implies repeated or ongoing action up to now (“you have been learning (repeatedly / over a period)”), not just the total amount achieved.

Tinhas aprendido (past perfect) would mean “you had learned” (before some other past point), which doesn’t fit here.

So já aprendeste is the natural choice to talk about the total amount learned up to that future day, and já adds the sense of “already”.

How do we know this is talking to tu (informal “you”) and not você?

Because of the verb endings:

hás de reler – hás is 2nd person singular of haver.
já aprendeste – aprendeste is also 2nd person singular of aprender in the preterite.

With você in European Portuguese, verbs conjugate in the 3rd person:

Você há de reler esse diário e ele há de lembrar‑lhe…
…de quanto já aprendeu.

So the original sentence is clearly addressed to someone with whom you use tu (informal, familiar).

Why is it esse diário and not este diário or aquele diário?

Portuguese distinguishes three deictic pronouns:

este – near the speaker (or “this, here/now”).
esse – near the listener, or something already known in the discourse.
aquele – far from both, often more distant in space or time.

Esse diário typically suggests:

“that diary (of yours / near you / that we’ve been talking about).”

Alternatives:

este diário – “this diary (here with me / just mentioned now).”
aquele diário – “that diary (over there / from way back then / more distant).”

In practice, many speakers don’t strictly follow the three‑way system all the time, but esse is very natural here to mean “that diary (you have / you know about)”.

Could the sentence be written with ir + infinitive instead of haver de + infinitive?

Yes. A very natural spoken European Portuguese version would be:

Um dia, vais reler esse diário e ele vai lembrar‑te de quanto já aprendeste.

Differences:

hás de / há de – slightly more literary / expressive, with a “one day, surely / inevitably” nuance.
vais / vai + infinitive – the default everyday future in speech.

Both are correct; the original just chooses a somewhat more “story‑like” tone.

What is the role of the hyphen in lembrar‑te?

The hyphen shows that te is an unstressed clitic pronoun attached to the verb:

lembrar + te → lembrar‑te

Basic rules relevant here:

When a clitic pronoun comes after an infinitive, gerund, or affirmative imperative verb in European Portuguese, it joins with a hyphen:
- lembrar‑te, ver‑te, ajudar‑te.
With a simple future or conditional, very formal written Portuguese can place the pronoun inside the verb (mesoclisis), also with hyphens:
- lembrar‑te‑á, lembrar‑se‑á, etc. (rare in everyday speech).

So the hyphen is just the standard spelling for attaching te to lembrar in this structure.