Learn Hardcore Indonesian: Di formulir itu, saya menulis tahun lahir saya.

In di formulir itu, it means “on that form” or “in that form”.
You use di to show a static location, similar to English “at/on/in” when nothing is moving:

di rumah – at home
di meja – on the table
di formulir itu – on that form

So here di just marks where the writing happens: on the form.

Why is the word order formulir itu and not itu formulir?

In Indonesian, demonstratives like itu (that) and ini (this) usually come after the noun:

buku itu – that book
rumah ini – this house
formulir itu – that form

Putting itu before the noun (itu formulir) is possible in speech, but it usually has a different function: it often works more like “that form (we were talking about)” with extra emphasis or as a topic.

For a simple noun phrase “that form” as part of a sentence, formulir itu is the normal, neutral order.

Is the comma after Di formulir itu necessary?

In everyday Indonesian writing, you will often see a comma after an initial phrase like Di formulir itu, but it’s not strictly required.

Di formulir itu, saya menulis tahun lahir saya.
Di formulir itu saya menulis tahun lahir saya.

Both are acceptable. The comma just helps show a short pause after the introductory phrase, similar to English.

Do I have to repeat saya in tahun lahir saya, or can I just say tahun lahir?

You don’t have to repeat saya. All of these are possible, depending on context:

Di formulir itu, saya menulis tahun lahir saya.
– Explicitly: “I wrote my year of birth.”
Di formulir itu, saya menulis tahun lahir.
– Literally: “I wrote the year of birth.”
This is okay if it’s obvious you are talking about your own birth year (for example, it’s your own form).

In many real situations, tahun lahir alone is enough because the form clearly belongs to you. Adding saya just makes it explicit.

Why is it tahun lahir saya and not tahun saya lahir?

Tahun lahir saya is a noun phrase:

tahun = year
lahir = birth (here used like “birth”/“born”)
saya = my

So tahun lahir saya = “my year of birth”.

Tahun saya lahir would be understood as “the year I was born” and feels more like a clause (a mini sentence) inside a bigger sentence, not a simple noun phrase.

In forms and short labels, Indonesian prefers the compact noun-phrase style:

tanggal lahir – date of birth
tempat lahir – place of birth
tahun lahir – year of birth

So tahun lahir saya matches this pattern and fits better in a form-filling context.

What exactly does tahun lahir mean literally?

Literally:

tahun = year
lahir = to be born / birth

Indonesian often uses a verb or adjective after a noun to qualify it. So:

tahun lahir = literally “birth year” or “year (of) being born”
tempat lahir = place of birth
tanggal lahir = date of birth

In English we usually say “year of birth”, but Indonesian naturally drops “of” and just puts the words together.

Can I say tahun kelahiran saya instead of tahun lahir saya?

Yes, tahun kelahiran saya is also correct and means the same thing: “my year of birth.”

lahir – to be born / birth (verb-like or basic form)
kelahiran – birth (noun derived with ke- -an)

Differences in nuance:

tahun lahir saya – common, neutral, slightly simpler/colloquial.
tahun kelahiran saya – a bit more formal or “bookish”.

In a form, tahun lahir is more typical, but both are understandable.

What is the difference between menulis and menuliskan? Could I say saya menuliskan tahun lahir saya?

Both menulis and menuliskan come from tulis (write).

menulis – to write
menuliskan – to write something for someone / to write something down (with a bit more focus on the object or the act of putting it in written form)

In your sentence:

Saya menulis tahun lahir saya. – completely natural.
Saya menuliskan tahun lahir saya. – also possible, often sounds a bit more “action-focused,” like “I wrote down my year of birth.”

In everyday speech and simple sentences, menulis is more common and perfectly fine here.

How do I know this sentence is past tense (“I wrote”) if there is no tense marker?

Indonesian verbs do not change form for tense. Menulis can mean:

I write
I am writing
I wrote
I have written

The tense is understood from context:

If you’re telling a story about yesterday, menulis will be understood as past.
If you’re explaining what you usually do, it will be understood as a habit.

If you want to make the past time clearer, you can add a time word:

Kemarin di formulir itu, saya menulis tahun lahir saya.
– Yesterday on that form, I wrote my year of birth.

Why is saya used here instead of aku? What is the difference?

Both saya and aku mean “I / me.”

saya – more formal and polite; used in writing, with strangers, in professional or neutral situations.
aku – more informal/intimate; used with friends, family, in casual conversation (depending on region and social group).

In a sentence about filling out a form, saya is more natural, because forms and anything related to official documents usually use the formal style.

The informal version could be:

Di formulir itu, aku menulis tahun lahirku.
(-ku is the informal possessive suffix for “my”.)

What does formulir mean? Are there other words for “form”?

Formulir means “form” as in an application form, registration form, official form.

Other related words:

formulir pendaftaran – registration form
formulir aplikasi – application form

You may also see form (an English loanword) in very informal settings or interfaces, but formulir is the standard Indonesian word for a document you fill in.

Is itu necessary in di formulir itu? What changes if I drop it?

No, itu is not strictly necessary. Compare:

Di formulir itu, saya menulis tahun lahir saya.
– On that form, I wrote my year of birth (specific form, already known in the context).
Di formulir, saya menulis tahun lahir saya.
– On the form, I wrote my year of birth (more general; the specific form is less clearly pointed out).

Using itu makes it sound like you and the listener both know which particular form you’re talking about (for example, “that registration form we mentioned”). Without itu, it’s a bit more generic.