Learn Hardcore Indonesian: Saya lupa tanggal rapat keluarga itu. - I forgot the date of that family meeting.

The subject (Saya) comes first.
The verb (lupa) comes next.
Then a noun phrase: tanggal rapat keluarga itu (literally the date [of] that family meeting), with the main noun (tanggal) first and its “of…” information after it.

Why is tanggal used here instead of hari or waktu?

Indonesian distinguishes these:

tanggal = a specific calendar date
- e.g. tanggal 10 Mei (May 10th)
hari = day (Monday, Tuesday, etc., or “day” in general)
- e.g. hari Senin (Monday), hari ini (today)
waktu = time (in a more general sense)
- e.g. waktu rapat (the time of the meeting), tidak punya waktu (don’t have time)

In Saya lupa tanggal rapat keluarga itu, you are saying you forgot the date (like the 15th, 20th, etc.), not which day of the week it is and not what clock time it starts.

If you wanted to say you forgot the time, you could say:

Saya lupa waktu rapat keluarga itu.
= I forgot the time of that family meeting.

Why isn’t there a word like “of” between tanggal and rapat?

Indonesian often shows “of” relationships simply by putting nouns next to each other.

tanggal rapat keluarga itu
literally: date meeting family that
meaning: the date of that family meeting

The pattern is:

Main noun first: tanggal (date)
Then the thing it belongs to: rapat keluarga itu (that family meeting)

There is no need for a separate word like of. The structure itself signals “the date of that family meeting”.

You could add a preposition like dari or a relative marker like yang, but it becomes less natural here. For example:

tanggal dari rapat keluarga itu – understandable, but sounds heavier and less idiomatic.
The simple tanggal rapat keluarga itu is what people normally say.

What exactly does itu refer to, and why is it at the end?

itu means that and marks something as specific/known to both speaker and listener.

In this sentence:

rapat keluarga itu = that family meeting (a particular meeting you both know about)

Word order:

Main noun: rapat (meeting)
Modifier: keluarga (family)
Determiner: itu (that)

So the structure is: rapat keluarga itu = that family meeting.

Why at the end? In Indonesian, determiners like itu (that) and ini (this) usually go after the noun phrase they modify:

rumah itu = that house
rapat keluarga itu = that family meeting
tanggal rapat keluarga itu = the date of that family meeting

So itu is attached to rapat keluarga, not directly to tanggal. You’re saying, “the date of that family meeting (the one we have in mind)”, not just “that date of a family meeting” in general.

Could I say tanggal itu rapat keluarga instead?

No, tanggal itu rapat keluarga is not a natural way to say this meaning.

tanggal itu rapat keluarga sounds like that date is a family meeting (and even then the grammar is off; you’d expect something like tanggal itu ada rapat keluarga).

To express “the date of that family meeting,” the normal pattern is:

tanggal rapat keluarga itu

Changing the order changes the structure and usually the meaning. So:

✅ tanggal rapat keluarga itu = the date of that family meeting
❌ tanggal itu rapat keluarga (not natural in this context)

Is it necessary to say Saya, or can I drop it and just say Lupa tanggal rapat keluarga itu?

You can drop Saya in casual conversation if the context already makes it clear that you are the one who forgot.

So:

Saya lupa tanggal rapat keluarga itu.
– Fully clear, neutral, suitable in most situations.
Lupa tanggal rapat keluarga itu.
– Sounds like “(I) forgot the date of that family meeting.”
Very common in speech, message chats, or when it’s obvious who is speaking.

Indonesian often omits pronouns when they’re understood from context. However, for learners and in more formal situations, keeping Saya is safer and clearer.

Are there alternative ways to say this sentence, like using dengan or akan?

Yes, you may see or hear variants like:

Saya lupa dengan tanggal rapat keluarga itu.
- Literally: I forgot with the date of that family meeting.
- Meaning: the same as the original, but dengan here is optional and makes it slightly more casual/colloquial in some varieties.
Saya lupa akan tanggal rapat keluarga itu.
- akan here is more formal or literary.
- You might find it in written or formal language, but it sounds stiff in everyday speech.

The most natural everyday version is still:

Saya lupa tanggal rapat keluarga itu.

How do we know this means “forgot” (past) and not “forget” (present) if there is no tense marker?

Indonesian verbs usually don’t change form for tense. The verb lupa can mean:

forget / am forgetting / forgot, depending on context.

In Saya lupa tanggal rapat keluarga itu, context supplies the time:

In real life, you use this when talking about a date you should already know or remember.
So listeners naturally understand it as “I forgot the date…” (a past event whose result is that you now don’t know/remember it).

If you want to make the time clearer, you can add time words:

Tadi saya lupa tanggal rapat keluarga itu.
= Earlier I forgot the date of that family meeting.
Kemarin saya lupa tanggal rapat keluarga itu.
= Yesterday I forgot the date of that family meeting.

But without extra words, Saya lupa… is normally understood as a past forgetting with a present effect.

What is the difference between lupa and melupakan?

Both come from the same root, but they’re used differently.

lupa – intransitive or directly with its object
- Saya lupa tanggal rapat.
  = I forgot the date of the meeting.
- The focus is that you don’t remember something.
melupakan – transitive verb, more like “forget something / leave something out / neglect something”
- Saya melupakan tanggal rapat itu.
  = I forgot that meeting date.
- This can sound a bit more deliberate or formal; it’s more common in writing or in a context of “overlooking / neglecting” something.

In everyday speech about memory, lupa is far more common:

✅ Saya lupa tanggal rapat keluarga itu. (natural)
⚠️ Saya melupakan tanggal rapat keluarga itu. (grammatically OK, but sounds more formal or like you “overlooked” it rather than just “it slipped my mind”.)

Is rapat keluarga treated as one unit like a compound noun?

Yes, rapat keluarga functions as a noun phrase:

rapat = meeting
keluarga = family
rapat keluarga = family meeting

The pattern [noun] + [noun] is very common in Indonesian and often acts like a single concept:

rapat keluarga = family meeting
rapat kerja = work meeting
rumah sakit = hospital (literally: sick house)
kartu kredit = credit card

So in tanggal rapat keluarga itu:

tanggal is the main noun (date)
rapat keluarga itu is a noun phrase modifying tanggal (which meeting’s date? that family meeting’s date)

Is this sentence polite and neutral, or does it sound rude or too casual?

Saya lupa tanggal rapat keluarga itu. is:

Neutral in tone
Polite enough for most situations
Suitable in both spoken and written Indonesian

If you want to sound a bit more polite or apologetic, you can add an apology:

Maaf, saya lupa tanggal rapat keluarga itu.
= Sorry, I forgot the date of that family meeting.

But the base sentence itself is neither rude nor too casual. It’s a standard, neutral statement.