Jamás olvidaré ese día.

Putting jamás first gives it emphasis. It makes the sentence sound stronger, a bit like stressing never in English.

So:

• Jamás olvidaré ese día. = emphatic, dramatic, firm
• No olvidaré jamás ese día. = also correct, slightly more neutral in structure

In Spanish, words like jamás and nunca can come before the verb and make the sentence negative by themselves, so you do not need no if they are placed before the verb.

They both usually mean never.

In many situations, they are interchangeable:

• Jamás olvidaré ese día.
• Nunca olvidaré ese día.

However, jamás often sounds a little:

• stronger
• more emphatic
• sometimes more literary or dramatic

Nunca is very common in everyday speech.
Jamás is also common, but it can feel more forceful here.

Olvidaré is the first person singular future tense of olvidar.

It comes from:

• olvidar = to forget
• olvidaré = I will forget

So the sentence means that in the future, the speaker says they will never forget that day.

Compare:

• olvido = I forget / I am forgetting
• olvidaré = I will forget
• olvidaría = I would forget

Here, olvidaré is the natural form for I will never forget.

Because Spanish often leaves out subject pronouns when the verb ending already shows who the subject is.

• olvidaré already means I will forget

So:

• Jamás olvidaré ese día. = normal and natural
• Yo jamás olvidaré ese día. = also correct, but yo adds emphasis

You might include yo if you want contrast, such as:

• Yo jamás olvidaré ese día, pero ellos sí.
  (I will never forget that day, but they will.)

These demonstratives show different kinds of distance.

• este día = this day, close to the speaker
• ese día = that day, somewhat removed, often already known in the conversation
• aquel día = that day over there / that day long ago, more distant

In this sentence, ese día is the natural choice for that day when referring to a specific day already in mind.

Very roughly:

• este = this
• ese = that
• aquel = that over there / that one further away / that one long ago

In real usage, ese is extremely common for that.

Because demonstratives such as este, ese, aquel already work like determiners. They normally replace the article.

So you say:

• ese día
• este libro
• aquella casa

Not:

• el ese día ❌

In English, you also don’t say the that day. Spanish works similarly here.

No. If jamás comes before the verb, it can negate the sentence by itself:

• Jamás olvidaré ese día. ✅

If it comes after the verb, Spanish normally uses no as well:

• No olvidaré jamás ese día. ✅

This is part of how Spanish negative words work.
Other examples:

• Nunca lo he visto.
• No lo he visto nunca.

But not normally:

• He visto nunca... ❌

So the position matters.

The accent mark shows the stressed syllable:

• ja-MÁS

Without the accent, jamas would not follow standard spelling for this word.

The written accent helps indicate pronunciation and correct stress.

There is also an accent in olvidaré:

• ol-vi-da-RÉ

That accent is also important because it shows the stress falls on the last syllable.

A simple approximation is:

• ja-MAS ol-vi-da-RE E-se DI-a

A few pronunciation notes:

• j in jamás is a strong throaty sound in Spanish, especially in Spain
• á and é show where the stress falls
• ese is pronounced roughly EH-se
• día has two syllables: DÍ-a

In Spain, the j is usually stronger and rougher than an English h.

It is two syllables:

• dí-a

The accent mark on í helps show that the i is pronounced separately from the a, instead of merging into one syllable.

So:

• día = two syllables
• not dya as one syllable

This is a very common feature in Spanish spelling.

Yes, that is correct.

These are all natural:

• Jamás olvidaré ese día.
• No olvidaré jamás ese día.
• No olvidaré ese día jamás.

They all mean basically the same thing, but the emphasis changes slightly.

• Jamás olvidaré ese día. → strongest emphasis on never
• No olvidaré jamás ese día. → very standard
• No olvidaré ese día jamás. → puts jamás at the end for emphasis there

Spanish often allows this kind of flexibility in word order.

It is grammatically the future tense, but in context it often sounds like:

• a firm statement
• a promise
• a declaration of strong feeling

So Jamás olvidaré ese día does mean I will never forget that day, but it can also carry the emotional force of:

• I’ll never, ever forget that day

So the future here is not just about time; it also expresses certainty and emotion.

Because ese día is a direct object referring to a thing, not a person.

Spanish uses the personal a mainly before specific human direct objects:

• Veo a María.
• Conozco a tu hermano.

But with things, you usually do not use a:

• Olvidaré ese día. ✅
• Olvidaré a ese día. ❌

Since día is a thing, no a is needed.

Yes. Although in this sentence it clearly means never, in other contexts jamás can sometimes be closer to ever, especially in more formal or literary language.

For example:

• Si jamás vuelves... = If you ever come back...

But in Jamás olvidaré ese día, the meaning is definitely never.

So for this sentence, you should understand it simply as a strong version of never.