Learn Hardcore Malay: Hari itu, saya pergi ke pejabat dengan bas.

If you said only hari, it would just mean day in a very general sense and would sound incomplete in this sentence. Hari itu points to a particular day in the past, similar to English on that day / that day.

Do I need to say pada hari itu instead of just hari itu?

Both are correct, but the nuance and register differ:

Hari itu, saya pergi ke pejabat dengan bas.
- Very natural in everyday speech and informal writing.
- The preposition pada is dropped, which is common.
Pada hari itu, saya pergi ke pejabat dengan bas.
- More formal and complete, often seen in essays, reports, news, or narratives.

In conversation, most people will just say Hari itu without pada.

How is past tense shown here? There’s no word for “went”, only pergi which looks like “go”.

Malay verbs do not change form for tense. Pergi can mean:

go (present/future): saya pergi = I go / I am going / I will go
went (past): saya pergi = I went

Past time is understood from:

Time words: hari itu, semalam (yesterday), tadi (earlier), etc.
Context, or optional markers like sudah, telah, dah (have/already).

So you could also say:

Hari itu, saya sudah pergi ke pejabat dengan bas.
Hari itu, saya telah pergi ke pejabat dengan bas.

These emphasize that the action had already happened, but your original sentence is already a perfectly natural past-tense statement in context.

Can I move hari itu to the end, like in English “I went to the office by bus that day”?

Yes. Both are grammatical and natural:

Hari itu, saya pergi ke pejabat dengan bas.
Saya pergi ke pejabat dengan bas hari itu.

Differences are subtle:

Putting Hari itu at the beginning slightly emphasizes the time of the event.
Putting hari itu at the end sounds more neutral, like just adding time information after the main statement.

In everyday conversation, both word orders are used.

What’s the difference between saya and aku? Why use saya here?

Both mean I / me, but their usage differs in politeness and context:

saya
- Polite, neutral, standard.
- Used with strangers, in formal situations, at work, in writing.
- Safe default pronoun for learners.
aku
- Informal, intimate, or casual.
- Used with close friends, family, sometimes in songs, poems, or when talking to children.
- Can sound rude or too familiar in formal contexts.

In your sentence, saya sounds polite and standard, suitable for most situations.

Why is it pergi ke pejabat and not pergi pejabat or pergi di pejabat?

Prepositions in Malay:

ke = to (movement towards a place)
di = at / in / on (location, no movement)

So:

pergi ke pejabat = go to the office (movement)
di pejabat = at the office (location)

Examples:

Saya pergi ke pejabat. = I go/went to the office.
Saya di pejabat. = I am at the office.

You can sometimes hear pergi pejabat in very casual speech, but pergi ke pejabat is the correct and standard form.

What does pejabat mean exactly? Could I say ofis instead?

pejabat = office (standard Malay, common in Malaysia & Brunei; in Indonesia, kantor is used).
ofis (from English office) is informal and colloquial.

Formal / standard: pejabat
Informal / casual speech: ofis (more common in spoken Malaysian Malay)

So in casual conversation, you might hear:

Hari itu, saya pergi ofis dengan bas.

But in writing, or if you want to sound standard, use pejabat.

In English, we say “by bus”, not “with bus”. Why does Malay use dengan bas (literally “with bus”)?

Yes, dengan literally means with, but in transport contexts it is used where English uses by:

dengan bas = by bus
dengan kereta = by car
dengan kapal terbang = by plane

So Hari itu, saya pergi ke pejabat dengan bas. is the natural way to say That day, I went to the office by bus.

The literal meaning is “with a bus”, but functionally it matches English by bus.

Is dengan bas the only way to say “by bus”? What about naik bas?

Both are common and natural, with a slight difference in feel:

dengan bas
- Focus on the method of transport (by bus).
naik bas (literally: “ride/climb bus”)
- Very common in everyday speech.
- Emphasizes the act of getting on / riding the bus.

You can say either:

Hari itu, saya pergi ke pejabat dengan bas.
Hari itu, saya pergi ke pejabat naik bas.

In casual spoken Malay, naik bas is extremely common and probably a bit more colloquial.

Can I use dengan for any way of travelling, like “by foot”?

You can often use dengan with vehicles, but Malay has some preferred expressions:

Vehicles:
- dengan bas = by bus
- dengan kereta = by car
- dengan teksi = by taxi
- dengan kereta api = by train
More idiomatic expressions:
- naik bas / naik kereta / naik teksi = ride a bus / car / taxi
- menaiki bas = a more formal version of naik bas
On foot:
- Typically berjalan kaki (on foot), not dengan kaki:
  - Saya pergi ke pejabat berjalan kaki. = I went to the office on foot.

So dengan is widely used for transport, but you should memorize common set phrases like berjalan kaki for “on foot”.

Why is there a comma after Hari itu? Is it always required?

The comma is mainly a writing convention:

When a time expression comes at the start, it’s common (and stylistically nice) to write a comma:
- Hari itu, saya pergi ke pejabat dengan bas.
In speech, you naturally pause a little after Hari itu.
In casual writing (texts, chats), people may drop the comma:
- Hari itu saya pergi ke pejabat dengan bas.

So the comma is good style and typical in formal writing, but not a strict grammar rule in everyday use.

Why isn’t there a word for “the” or “a” like in English “the office” or “a bus”?

Malay has no articles like a, an, the. Nouns are generally bare:

pejabat = office / the office / an office (depending on context)
bas = bus / the bus / a bus

Specificity is understood from context or added words if needed:

sebuah pejabat = an office / one office
pejabat itu = that office / the office
sebuah bas = a bus / one bus
bas itu = that bus / the bus

In your sentence, we understand from context that it’s the office and by bus without any article words.

How would this sentence sound if I made it more formal or more casual?

Original (neutral, standard):

Hari itu, saya pergi ke pejabat dengan bas.

More formal:

Pada hari itu, saya telah pergi ke pejabat dengan menaiki bas.
- pada adds formality.
- telah is a formal past marker.
- menaiki bas is more formal than naik bas.

More casual / spoken Malaysian style:

Hari tu, aku pergi ofis naik bas.
- Hari tu = colloquial form of Hari itu.
- aku instead of saya (informal “I”).
- ofis instead of pejabat (loanword, casual).
- naik bas is the common spoken phrasing.

The original sentence is a good, safe, standard version suitable for learners.