Ožujak mi je drag, ali ono što stvarno volim u travnju jesu dugi, svijetli dani.

Literally, it means March is dear to me.

Breaking it down:

• Ožujak = March
• mi = to me
• je = is
• drag = dear, liked, pleasant to someone

So Croatian often uses an adjective plus a dative pronoun where English would more naturally use I like.... A natural English translation is simply I like March.

Both are possible, but they are not exactly the same in tone.

• Ožujak mi je drag sounds warm, personal, and a little gentler.
• Volim ožujak is more direct: I love / I really like March.

In Croatian, drag is very common when talking about things, people, times, places, etc. that you feel fond of. So this sentence sounds natural and a bit more nuanced than a plain volim sentence.

Mi is the dative form of ja and means to me.

With adjectives like drag, Croatian often marks the person experiencing the feeling in the dative:

• On mi je drag = He is dear to me / I like him
• Ovo mi je važno = This is important to me
• Ožujak mi je drag = March is dear to me

So mi is not optional decoration; it tells you who finds March pleasant or dear.

Ono što literally means that which, but in normal English it is usually just what.

So:

• ono što stvarno volim u travnju = what I really love in April

This is a very common Croatian structure. It introduces a whole idea and turns it into something like a noun phrase.

Examples:

• Ono što želim = What I want
• Ono što znam = What I know
• Ono što volim = What I love

Because after u meaning in, Croatian normally uses the locative case for location or time.

So:

• dictionary form: travanj = April
• locative form: travnju
• u travnju = in April

This is the standard case change you need after u in this kind of meaning.

It is locative singular.

The noun is travanj in the nominative, but after u it changes:

• travanj = April
• u travnju = in April

So if you are learning cases, this is a good example of a time expression in the locative.

Because in this kind of identifying sentence, Croatian often makes the verb agree with the noun phrase that comes after it:

• dugi, svijetli dani = long, bright days

Since dani is plural, the verb appears in the plural:

• jesu

So the structure is roughly:

• What I really love in April are long, bright days

This is one place where Croatian works differently from English. English often uses singular is in this pattern, but Croatian very naturally uses plural agreement with dani here.

Jesu is the full, stressed form of the verb, while su is the short clitic form.

• jesu = full form
• su = short unstressed form

In this sentence, jesu sounds a bit more deliberate and slightly more emphatic. It also fits well stylistically after the longer clause ono što stvarno volim u travnju.

You may also hear su in similar sentences in everyday speech, but jesu is perfectly natural and often preferred in a sentence like this.

Because they have to agree with dani.

• dani = days, nominative masculine plural
• dugi = long, nominative masculine plural
• svijetli = bright, nominative masculine plural

Croatian adjectives agree with the noun in gender, number, and case. Since dani is masculine plural, both adjectives also appear in masculine plural.

Here svijetli means bright or full of light.

With days, it refers to there being a lot of daylight, not to color. So:

• svijetli dani = bright days

It does not mean light-colored days.

In Croatian, names of months are normally written with a lowercase letter:

• ožujak
• travanj

Here Ožujak is capitalized only because it is the first word of the sentence. Later in the sentence, travnju stays lowercase, which is the normal Croatian spelling.

Yes. Croatian traditionally uses its own Slavic month names, such as:

• ožujak = March
• travanj = April

This is one thing that makes Croatian look different from some neighboring standard languages, where international forms like mart and april are more common.

Yes. Croatian word order is flexible.

A more straightforward version would be:

• Ožujak mi je drag, ali u travnju stvarno volim duge, svijetle dane.

That version is simpler and more direct.

The original sentence:

• Ožujak mi je drag, ali ono što stvarno volim u travnju jesu dugi, svijetli dani.

puts extra focus on dugi, svijetli dani. It sounds a bit more shaped and expressive, almost like: What I really love in April is the long, bright days.

There are two different reasons.

1. Before ali

   • ali = but
   • Croatian normally puts a comma before ali when it joins clauses.

2. Between dugi and svijetli

   • This comma separates two coordinate adjectives: long, bright days
   • It shows that both adjectives describe the noun separately and with equal weight

So the punctuation is doing the same kind of job it often does in English.