Learn Hardcore Romanian: Programul de seară se termină târziu, după culcare. - The evening schedule ends late, after bedtime.

de here functions like of or for, turning seară (evening) into a descriptive phrase: de seară ≈ evening, for the evening, evening-time.
It’s a very common way in Romanian to form “type-of” phrases:

program de seară – evening program
rochie de vară – summer dress
mâncare de prânz – lunch food

So Programul de seară literally is “the program of evening / for the evening,” i.e. the evening program.

Why seară and not seara in de seară?

seară = evening (indefinite form)
seara = the evening (definite form, with the article attached)

In the pattern de + noun used adjectivally (program de seară, rochie de vară), the noun normally stays in its basic (indefinite) form.
You would not say program de seara in this meaning; that would sound wrong or at least very odd to native speakers.

Is de seară the same as saying seral?

They’re related in meaning, but not used in exactly the same way.

program de seară is the natural, everyday way to say evening program.
seral is an adjective (from Latin) often used in more specific contexts, like cursuri serale (evening classes).

You wouldn’t normally say program seral in this general TV‑ or event‑schedule sense; program de seară is the standard expression.

Why do we say se termină and not just termină?

With the meaning to come to an end / to be over, a se termina is used reflexively:

Programul se termină. – The program ends.

Without se, a termina is normally transitive (to finish something):

Ei termină programul. – They finish the program.

So for “the program ends,” Romanian prefers Programul se termină, not Programul termină.

What exactly does se do in se termină?

se is a reflexive clitic pronoun used here to form a middle / reflexive verb: a se termina.
It doesn’t literally mean “itself” in this context; instead it turns a termina (to finish something) into a se termina (to be finished / to come to an end).
This pattern is very common with Romanian verbs:

a deschide – to open (something) → a se deschide – to open / to be opened
a opri – to stop (something) → a se opri – to stop / to come to a stop

What part of speech is târziu, and how is it used?

Here târziu is an adverb meaning late.
It typically goes after the verb: se termină târziu – ends late.
Related forms:

târzie (fem. sg. adjective) – a late hour → o oră târzie
târzii (adj. pl.) – late nights → seri târzii

As a bare form after the verb, it’s adverbial: ajung târziu, plec târziu, se termină târziu.

How is târziu pronounced, especially â?

Approximate pronunciation: târziu ≈ tər-ZEE-oo (said fairly quickly).
Key points:

â is a central vowel, similar to the French un or the a in English sofa, but more closed; it never sounds like English oo or ee.
ziu is like zee-oo run together.
Stress is on -ziu: târZIU.

What does după culcare literally mean, and why no article?

după culcare literally means after going to bed / after bedtime.
culcare is a verbal noun from the verb a (se) culca (to put to bed / to go to bed).

Like many verbal nouns, when you talk about the activity in general, you use it without an article:

la culcare – at bedtime
după cină – after dinner
înainte de plecare – before leaving

So după culcare = after the act of going to bed, understood from context as “after (someone’s) bedtime.”

Is culcare related to a se culca?

Yes.

a (se) culca = to put (someone) to bed / to go to bed
culcare = the act of going to bed / the act of putting to bed

So:

Ora de culcare – bedtime
după culcare – after going to bed
They’re the same lexical family; culcare is the noun form of the verb.

Could I say după ce mă culc instead of după culcare?

You can, but the nuance changes:

după culcare is neutral and impersonal: after bedtime / after going to bed (who exactly goes to bed is left implicit or understood from context).
după ce mă culc = after I go to bed – it explicitly refers to me.

So if you mean “The evening program ends late, after my going to bed,” you might say:
Programul de seară se termină târziu, după ce mă culc.
The original sentence sounds more general, like “after (our / the usual) bedtime.”

Why is there a comma before după culcare?

The comma separates the main clause from a following adverbial phrase that adds extra information:

Main clause: Programul de seară se termină târziu
Adverbial phrase: după culcare

Romanian commonly uses a comma before such short adverbials when they are felt as an afterthought or clarification, similar to English:

“The show ends late, after bedtime.”

You could also write it without a comma (…se termină târziu după culcare); with the comma, the pause and emphasis on “after bedtime” is a bit stronger.