Ya sea por la mañana o por la noche, la editora revisa cada titular con calma.

Ya sea ... o ... is a set expression meaning whether ... or ....

So:

• Ya sea por la mañana o por la noche = Whether in the morning or at night

It presents two alternatives, but the main action happens in either case.

You will often see similar patterns such as:

• Ya sea en casa o en la oficina = whether at home or in the office
• Ya sea solo o acompañado = whether alone or with company

It is a slightly more formal or polished way to speak than some simpler alternatives.

Sea is the subjunctive form of ser.

The expression ya sea ... o ... always uses the subjunctive, because it introduces alternatives rather than stating a simple fact with ser.

So you should learn ya sea as a fixed chunk:

• ya sea A o B

Not:

• ya es A o B ❌

This is one of those cases where it is often easiest to memorise the whole expression rather than trying to build it from scratch every time.

Por la mañana means in the morning.

In Spanish, parts of the day are very often expressed with por:

• por la mañana = in the morning
• por la tarde = in the afternoon / evening
• por la noche = at night / in the evening

This is just the normal idiomatic way to talk about these time periods.

A learner may expect a direct equivalent of English in, but Spanish uses por in these common expressions.

Spanish normally uses the definite article with parts of the day in expressions like these:

• por la mañana
• por la tarde
• por la noche

So even though English says in the morning and at night, Spanish keeps the article.

This is very natural and standard. Omitting the article would sound wrong here.

The comma separates the opening time expression from the main clause.

The sentence has this structure:

• Ya sea por la mañana o por la noche, = introductory phrase
• la editora revisa cada titular con calma. = main clause

In English, we often do the same thing with an opening phrase:

• Whether in the morning or at night, the editor reviews each headline calmly.

The comma makes the sentence easier to read and shows where the main statement begins.

La editora is the feminine form, meaning the female editor.

In Spanish, many professions have masculine and feminine forms:

• el editor = male editor
• la editora = female editor

In modern usage, editora is standard for a woman working as an editor or publisher, depending on context.

So this sentence specifically refers to a female editor.

Revisa comes from revisar, which usually means:

• to review
• to check
• to inspect

Here, la editora revisa cada titular suggests that she checks/reviews each headline carefully.

It is in the present tense, third person singular:

• yo reviso
• tú revisas
• él/ella revisa

So revisa = she reviews/checks.

Cada titular means each headline or every headline.

Cada is used with a singular noun:

• cada titular
• cada página
• cada día

It focuses on the items one by one.

By contrast:

• todos los titulares = all the headlines

Both can sometimes be translated similarly in English, but the nuance is slightly different:

• cada titular = each individual headline
• todos los titulares = all the headlines as a group

Here, cada titular suggests careful attention to one headline at a time.

Because cada is followed by a singular noun in Spanish.

So you say:

• cada titular
• cada libro
• cada persona

Not:

• cada titulares ❌

Even though English may translate this as every headline or each headline, Spanish keeps the noun singular after cada.

Con calma literally means with calm, but in natural English it often corresponds to:

• calmly
• carefully
• without rushing

So in this sentence, it means the editor reviews each headline in a calm, unhurried way.

Spanish often uses a prepositional phrase where English might prefer an adverb:

• Habla con calma = He/She speaks calmly
• Trabaja con paciencia = He/She works patiently

So yes, it can function much like calmly, though the Spanish expression feels slightly more like in a calm manner.

Yes, tranquilamente is possible, but it is not exactly identical in tone.

Compare:

• con calma = calmly, without hurry, in a relaxed way
• tranquilamente = calmly, peacefully, tranquilly

In many contexts they are close, but con calma is extremely common and idiomatic when talking about doing something carefully and without rushing.

So:

• La editora revisa cada titular con calma sounds very natural.

This is the normal Spanish word order:

• Subject: la editora
• Verb: revisa
• Object: cada titular
• Manner expression: con calma

So literally:

• the editor reviews each headline calmly

Spanish word order can sometimes be flexible, but this version is the most neutral and straightforward.

For example, you could move con calma earlier for emphasis:

• La editora revisa con calma cada titular

That is also correct, but the original sentence sounds very natural.

Yes. Revisa is in the present indicative, and here it most naturally describes a habitual action.

So the sentence suggests something like:

• She reviews each headline calmly, whether in the morning or at night.

Spanish present tense often covers what English expresses with the simple present for routines or repeated actions.

Yes, depending on context, por la noche can cover both in the evening and at night.

Spanish does not always divide evening and night in exactly the same way English does. In many contexts:

• por la tarde = in the afternoon / early evening
• por la noche = in the evening / at night

So the exact English translation depends on the situation. In this sentence, either may work depending on how late the editor is working.