Learn Hardcore Indonesian: Setelah hari yang panjang itu, kami tidur dengan tenang, dan di buku harian saya menulis, “Hari ini penuh binatang, roket, dan imajinasi.” - After that long day, we sleep peacefully, and in my diary I write, “Today was full of animals, rockets, and imagination.”

Setelah means after. It introduces something that happens following another event, so Setelah hari yang panjang itu is After that long day.

You can also use sesudah here: Sesudah hari yang panjang itu.

Setelah and sesudah are near‑synonyms and are both very common.
Setelah is slightly more common in writing and may feel a bit more neutral/formal.
In everyday conversation, you will hear both without a big difference in meaning.

So in this sentence, setelah and sesudah are both correct.

How does hari yang panjang itu work grammatically? Why is yang used?

Break it down:

hari = day
yang panjang = that is long / which is long
itu = that (a determiner pointing to a specific thing already known)

So hari yang panjang itu literally feels like the day that was long, that one, which we translate naturally as that long day.

Yang links a noun (hari) with a description (panjang) and effectively turns the description into a clause (yang panjang = that is long). It:

marks the start of a descriptive phrase or relative clause,
makes it very clear that panjang is describing hari,
adds a slightly more descriptive, story‑like feel than just hari panjang itu.

So hari yang panjang itu is a very natural, slightly narrative way to say that long day.

Could I say hari panjang itu without yang? Would that be wrong or change the meaning?

Hari panjang itu is not wrong; Indonesians will understand it. It still means that long day.

Differences in feel:

hari panjang itu
- simpler, a bit more like just long day that;
- can sound slightly more neutral and less “story‑like.”
hari yang panjang itu
- sounds a bit more descriptive and literary, fitting a narrative;
- emphasizes the quality panjang as an important feature of that day.

In many cases, both are fine, but in storytelling, hari yang panjang itu often sounds more natural and expressive.

Why is kami used instead of kita for we?

Indonesian has two forms of we:

kami = we (but not you) — exclusive
kita = we (including you) — inclusive

In kami tidur dengan tenang, the speaker is talking about a group that does not include the listener. For example, the narrator and their family, or the narrator and friends.

If the speaker wanted to include the person they are talking to (for example, retelling the story to someone who was also there), they would use kita: kita tidur dengan tenang.

So kami is correct here because the listener is not part of that group.

What does dengan tenang literally mean, and why not just tenang?

Literally:

dengan = with
tenang = calm

So dengan tenang is literally with calm, and functionally it means calmly / peacefully.

In Indonesian, dengan + adjective often functions like an adverb in English:

berjalan dengan pelan = to walk slowly
berbicara dengan jelas = to speak clearly
tidur dengan tenang = to sleep calmly / peacefully

You can say tidur tenang, and that is also understandable, but:

tidur dengan tenang sounds like natural, standard Indonesian.
tidur tenang can work, but sometimes sounds a bit more like a fixed phrase (and in some contexts it can be used in euphemisms like rest in peace).
Another very common expression is tidur nyenyak, meaning sleep soundly.

So in this sentence, tidur dengan tenang nicely expresses we slept peacefully.

In di buku harian saya menulis, what does di mean, and is di buku harian the same as dalam buku harian?

Di is a basic location preposition, usually meaning in / at / on, depending on context.

di buku harian here means in (my) diary.

You could also say dalam buku harian, which literally means inside the diary.

Nuance:

di is more general for location: di rumah (at home), di meja (on the table).
dalam emphasizes inside something: dalam kotak (inside the box).

In practice, di buku harian and dalam buku harian are both acceptable here, with only a small nuance difference. Di buku harian is more common and sounds very natural.

Why is the word order di buku harian saya menulis and not saya menulis di buku harian? Are both correct?

Both word orders are grammatically correct:

Saya menulis di buku harian = I wrote in (my) diary.
Di buku harian saya menulis = In (my) diary I wrote.

The difference is emphasis and flow:

Saya menulis di buku harian is the neutral order: subject (saya) first, then verb, then location.
Di buku harian saya menulis puts di buku harian at the beginning to highlight the place (the diary) as the topic, then says what happened there.

In narratives, it is quite common to front a phrase like this for variety and rhythm. Here it connects smoothly with the previous part:
... kami tidur dengan tenang, dan di buku harian saya menulis ...

So yes, both are correct; the chosen order gives a slightly more narrative feel.

How is past tense shown in kami tidur and saya menulis? There is no word like did or a past ending.

Indonesian verbs do not change form for past, present, or future. The basic form:

tidur = sleep / slept / will sleep, depending on context
menulis = write / wrote / will write

Tense and time are shown by:

time expressions: kemarin (yesterday), tadi malam (last night), besok (tomorrow)
context: narrative flow, things that have already been mentioned
optional aspect words:
- sudah (already)
- sedang (currently)
- akan (will)

In this sentence:

Setelah hari yang panjang itu (after that long day) clearly sets a past narrative.
Because of that, kami tidur and saya menulis are naturally understood as we slept and I wrote without needing any extra marker.

In the diary sentence Hari ini penuh binatang, roket, dan imajinasi, why is there no verb like adalah?

In Indonesian, when the predicate is an adjective or a stative word, you normally do not need a separate verb like to be.

Here:

Hari ini = today / this day
penuh = full (of)

So Hari ini penuh binatang, roket, dan imajinasi literally works as Today full of animals, rockets, and imagination, which is understood as Today is full of animals, rockets, and imagination.

You generally do not say:

Hari ini adalah penuh ... → this sounds wrong or very unnatural.

Adalah is mainly used before nouns or noun phrases in more formal contexts, for example:

Jakarta adalah ibu kota Indonesia. = Jakarta is the capital of Indonesia.

But with adjectives or words like penuh, Indonesian simply omits the to be verb.

Does binatang, roket, dan imajinasi mean animals, rockets, and imagination in plural, even though there is no plural ending?

Yes. Indonesian usually does not mark plural nouns the way English does.

binatang can mean animal or animals, depending on context.
roket can mean rocket or rockets.
imajinasi is like English imagination (often uncountable).

Plurality is understood from context or emphasized with extra words if needed:

banyak binatang = many animals
beberapa roket = several rockets

In Hari ini penuh binatang, roket, dan imajinasi, the natural reading is plural: full of animals, rockets, and imagination. The language doesn’t need plural endings to convey that.

What is the function of itu and ini in hari yang panjang itu and Hari ini? Why itu in one place and ini in the other?

Ini and itu are demonstratives:

ini = this (near to the speaker in time/space, or current)
itu = that (more distant in time/space, or already completed/known)

In the sentence:

hari yang panjang itu = that long day
- itu points back to a day that has already finished, a day we’re looking back on.
Hari ini penuh binatang, roket, dan imajinasi = Today is full of animals, rockets, and imagination.
- hari ini is a very common fixed expression meaning today (literally this day).

So:

itu is used for that day just ended.
ini inside the diary entry reflects the speaker’s perception at the time of writing: for the writer in the diary, it is this day / today.

This contrast nicely shows the narrator in the present (of the story) looking back at what they wrote during that day.

Could I replace buku harian with diari? Are they the same?

Yes, they are very close in meaning.

buku harian
- literally daily book;
- fully Indonesian (native words);
- very common and clear.
diari
- a loanword (from diary);
- also widely understood and used;
- can sound a bit more modern or casual depending on context.

You could say:

di buku harian saya menulis ...
di diari saya menulis ...

Both mean in my diary I wrote ....

If you want to be completely neutral and clear, buku harian is a very safe choice.

Is the comma before dan in binatang, roket, dan imajinasi required in Indonesian? Does Indonesian use a serial (Oxford) comma?

In Indonesian, the comma rules in lists are similar to English, but the serial (Oxford) comma before dan is more flexible and often not used.

Standard guideline for simple lists:

Saya membeli apel, jeruk dan pisang.
- With no comma before dan (this is very common).

In your sentence:

binatang, roket, dan imajinasi

The comma before dan is not wrong; some writers use it, especially to mirror English style or for clarity. But many style guides would prefer:

binatang, roket dan imajinasi

So:

The first commas in the list (binatang, roket) are required to separate items.
The final comma before dan is optional and depends on stylistic choice and the style guide being followed.

In saya menulis, “Hari ini penuh binatang, roket, dan imajinasi.”, is this direct speech? Is the punctuation and capitalization like in English?

Yes, this is direct quotation of what the speaker actually wrote in the diary.

Punctuation and capitalization here closely follow English‑style conventions:

A comma after menulis introduces the quoted sentence.
The quoted sentence Hari ini penuh binatang, roket, dan imajinasi. starts with a capital H, just like a normal sentence.
The full stop (period) goes inside the quotation marks.

Indonesian writing often uses this same pattern for quoting someone’s exact words, especially in modern and published texts.