Tuvimos un día horrible.

Tuvimos is the preterite form of tener for nosotros: we had.

A useful quick breakdown:

• tener = to have
• preterite stem = tuv- (irregular)
• ending for nosotros in the preterite = -imos

So:

• yo tuve
• tú tuviste
• él/ella/usted tuvo
• nosotros tuvimos
• vosotros tuvisteis
• ellos/ellas/ustedes tuvieron

So tuvimos means we had.

Because tener is irregular in the preterite.

In the present tense, you see the stem ten-:

• tenemos
• tienen

But in the preterite, tener changes to the stem tuv-:

• tuve
• tuviste
• tuvo
• tuvimos

So tuvimos is not built from the normal ten- stem. It uses the special preterite stem tuv-.

Because tuvimos presents the day as a completed past event.

Spanish often uses the preterite for things seen as finished wholes:

• Tuvimos un día horrible. = We had a horrible day.

If you used the imperfect, teníamos, it would usually sound more like:

• a repeated situation in the past
• background description
• or something ongoing, depending on context

For example:

• En ese trabajo, siempre teníamos días horribles.
  = In that job, we always had horrible days.

So in your sentence, the speaker is talking about one specific finished day, which is why tuvimos fits best.

Because Spanish often leaves out subject pronouns when the verb form already makes the subject clear.

Here, tuvimos already tells you the subject is we.

So:

• Tuvimos un día horrible. = normal and natural
• Nosotros tuvimos un día horrible. = possible, but more emphatic

You might include nosotros if you want contrast, for example:

• Ellos se divirtieron, pero nosotros tuvimos un día horrible.
  = They had fun, but we had a horrible day.

Because día is masculine, even though it ends in -a.

So you say:

• un día
• el día
• este día

This is one of those common Spanish nouns that do not follow the usual ending pattern.

A few examples:

• un día largo
• el día siguiente
• un día horrible

So the article must be un, not una.

The accent in día shows that the í is stressed and that día is pronounced in two syllables:

• dí-a

Without the accent, the vowel combination could be read differently. The written accent helps show that this is not a single-syllable diphthong, but a clear two-syllable word.

So:

• día = DEE-ah

This is why the accent mark is necessary.

Because in Spanish, descriptive adjectives usually come after the noun.

So the neutral, standard order is:

• un día horrible

That is the most natural way to say a horrible day.

You can sometimes place the adjective before the noun:

• un horrible día

But that sounds more literary, dramatic, or emphatic. It is less neutral than un día horrible.

So for ordinary speech, un día horrible is the normal choice.

It changes for number, but not normally for gender in the singular.

Examples:

• un día horrible
• una noche horrible

Same form in both masculine and feminine singular: horrible

In the plural, it becomes:

• días horribles
• noches horribles

So the pattern is:

• singular: horrible
• plural: horribles

A simple pronunciation guide would be:

too-BEE-mos oon DEE-ah o-RREE-bleh

A few helpful details:

• h in horrible is silent
• rr in horrible is a strong rolled or trilled r
• v in tuvimos sounds very similar to Spanish b
• día has two syllables: DEE-ah

So the rhythm is roughly:

tu-VI-mos un DÍ-a ho-RRI-ble

Yes. Pasamos un día horrible is also very natural.

There is a slight nuance:

• Tuvimos un día horrible = We had a horrible day.
• Pasamos un día horrible = We spent/went through a horrible day.

Both are good Spanish. In many situations, they are very close in meaning.

You could also hear:

• Fue un día horrible. = It was a horrible day.

That version shifts the structure a bit, but the overall idea is still very similar.

Yes, it is a very close cognate. It means basically the same thing as English horrible.

That makes it easy to recognise, but remember the Spanish pronunciation is different:

• silent h
• rolled rr
• final e pronounced

So although it looks familiar, it should sound Spanish when spoken: o-RREE-bleh.

Yes. In Spanish, tener un día horrible works much like English to have a horrible day. It means to experience that kind of day.

So tener here is not about possession in a literal sense. It is about what kind of day someone experienced.

That is why the sentence sounds completely natural in Spanish.