A época mudou tudo.

Because época is a feminine singular noun, so it normally takes the feminine singular article a when you mean the.

• a época = the era / the period / the time
• uma época = an era / a period / a time

In this sentence, a época is the subject.

Época usually means something like:

• era
• period
• time
• phase

It often refers to a stretch of time with some defining character.

For English speakers, it can look like epoch, but in everyday Portuguese época is more common and broader than the English word epoch. Depending on context, it can sound very natural where English would use the times, that period, or that era.

Mudou is the preterite form of the verb mudar for ele / ela / você.

Conjugation:

• eu mudei
• você/ele/ela mudou
• nós mudamos
• eles/elas/vocês mudaram

Since a época is a singular noun, the verb is in 3rd person singular:

• A época mudou tudo.

The preterite is used because it presents the change as a completed event: it changed everything.

Because mudou and mudava express different kinds of past meaning.

• mudou = changed, seen as a completed action
• mudava = used to change / was changing, more ongoing, habitual, or backgrounded

So:

• A época mudou tudo. = That era changed everything.
• A época mudava tudo. would sound more like That period used to change everything or was changing everything, which is much less likely in this kind of sentence.

Because tudo means everything.

Compare:

• tudo = everything
• todo = every / all, used before a noun in the singular
• todos = all, usually plural

Examples:

• mudou tudo = changed everything
• todo dia = every day
• todos os dias = all the days / every day

So in your sentence, tudo is correct because it stands alone as a pronoun meaning everything.

Because tudo is an indefinite pronoun, not a regular noun here. It already means everything, so it does not take an article in normal usage.

You say:

• Tudo mudou. = Everything changed.
• A época mudou tudo. = The era changed everything.

Not:

• o tudo in this meaning

Yes.

The sentence breaks down like this:

• A época = subject
• mudou = verb
• tudo = direct object

So literally the structure is:

• The era
  • changed
    • everything

That is why the verb is singular: it agrees with a época.

Yes, but the meaning or emphasis may shift slightly.

Normal order:

• A época mudou tudo.

Other possible orders:

• Tudo mudou na época. = Everything changed in that period.
  This is a different structure and not exactly the same meaning.
• Mudou tudo naquela época. = Everything changed in that era.
  Again, this changes the subject and meaning.

If you want to say that the era/time period itself changed everything, then A época mudou tudo is the clearest structure.

In Brazilian Portuguese, it is pronounced approximately:

• EH-po-ka

The stress is on the é:

• Épo-ca

That accent mark tells you the stressed syllable.

A rough English-friendly guide:

• é like e in bet
• po like po in poh, but shorter
• ca like kah

The accent in época marks the stressed syllable and shows that the vowel is pronounced openly.

So:

• época → stress on the first syllable: É-po-ca

Without the accent, Portuguese spelling rules would suggest a different stress pattern, so the accent is necessary.

Usually not in the sense of spring/summer/fall/winter. For that, Portuguese normally uses estação.

• estação do verão = summer season
• época = period / era / time

However, época can sometimes mean season in a broader sense, like harvest season or holiday season, depending on context:

• época de chuva = rainy season
• época de Natal = Christmas season / Christmastime

In your sentence, era / period / time is the natural reading.

Yes, often you can, but be careful.

Portuguese época is more like:

• period
• era
• phase
• time period

It is not the general word for time. The general word is tempo.

Compare:

• Não tenho tempo. = I don’t have time.
• Naquela época... = In that time / In those days / Back then...

So época can be translated as time in some contexts, but specifically as a period of time.

Not necessarily. Both can work, but they are not always identical.

• época is very common and flexible for period / time / era
• era can sound a little more historical or more specifically like a defined era

Examples:

• Naquela época = Back then / In those days
• na era digital = in the digital age

So A época mudou tudo is perfectly natural, depending on the context. It may suggest the times or that period rather than a formally named historical era.

Yes, it can be natural, especially in a reflective, historical, or literary context.

It sounds like:

• the times changed everything
• that period changed everything
• the era changed everything

In everyday speech, the exact wording depends on context. Brazilians might also say things like:

• Naquela época, tudo mudou. = Back then, everything changed.
• Aquele período mudou tudo. = That period changed everything.
• Os tempos mudaram tudo. = The times changed everything.

But your original sentence is grammatically correct and natural.