Learn Hardcore Indonesian: Siaran itu dimulai pukul delapan. - That broadcast starts at eight o'clock.

Itu marks specificity: think “the/that.” Siaran itu = “that/the broadcast (we both know).” Without it (Siaran dimulai…) the noun is more general/unspecified but still grammatical. You can also use ini (“this”) or, in formal writing, tersebut (“the aforementioned”): Siaran tersebut dimulai…

Why use dimulai instead of mulai or memulai?

mulai = “start” (intransitive): Siaran itu mulai pukul delapan.
memulai = “to start (something)” (active, transitive): Panitia memulai siaran pukul delapan.
dimulai = passive (“is started”): Siaran itu dimulai pukul delapan. In schedules/announcements, Indonesian often prefers dimulai to foreground the event/time rather than the doer.

Is dimulai passive? Who’s the agent?

Yes. di- marks the passive: di- + mulai → dimulai (“be started”). The agent is usually irrelevant/omitted, but you can add one with oleh: Siaran itu dimulai oleh stasiun TV pukul delapan.

Do I need the preposition pada before the time?

No. Time expressions commonly appear without it: …dimulai pukul delapan. Adding pada is fine and a bit more formal: …dimulai pada pukul delapan.

What’s the difference between pukul and jam?

Both mean “o’clock,” but:

pukul is more formal/announcement style: pukul 08.00
jam is neutral/everyday: jam delapan Either works here: Siaran itu dimulai jam delapan.

Does pukul delapan mean 8 a.m. or 8 p.m.? How do I specify?

By itself it’s ambiguous. Specify with a time-of-day word:

pukul delapan pagi (~morning)
pukul delapan malam (~evening) Indonesians also use the 24‑hour clock: pukul 20.00 = 8 p.m. Common ranges: pagi (~4–11), siang (~11–15), sore (~15–18), malam (after ~18), dini hari (very early morning).

How do I say “exactly at eight” or “about eight”?

Exactly: tepat pukul delapan, pas jam delapan (colloquial)
About: sekitar/kira-kira pukul delapan, kurang lebih jam delapan

How do I say 8:15, 8:30, and 8:45?

8:15: pukul delapan lima belas; or jam delapan lewat lima belas; or jam delapan lewat seperempat
8:30: pukul delapan tiga puluh; or idiomatically jam setengah sembilan (“half to nine” = 8:30)
8:45: pukul delapan empat puluh lima; or jam sembilan kurang seperempat

Can I move the time to the front?

Yes. Time adverbials can be fronted:

Pukul delapan, siaran itu dimulai.
Siaran itu dimulai pukul delapan. Both are natural. Fronting adds emphasis to the time.

Is di- here the same as the separate preposition di (“in/at/on”)? How do I spell it?

No. The passive prefix di- attaches to the verb with no space: dimulai. The preposition di is separate and followed by a location: di rumah. Avoid the common error di mulai (incorrect).

Is siaran the right word? How does it differ from acara, tayangan, or program?

siaran = a broadcast (the act/instance of broadcasting, usually radio/TV)
acara = a show/event/program (most general)
tayangan = a telecast/airing (the content shown)
program = a program/show (often borrowed, media context) You could also say Acara itu dimulai pukul delapan.

How do I indicate past or future? Indonesian doesn’t mark tense here.

Add time/aspect words:

Future: Siaran itu akan dimulai pukul delapan.
Completed: Siaran itu sudah/telah dimulai. Without them, context decides whether it’s a schedule, a current fact, or a report.

Can I just write Dimulai pukul delapan on a poster?

Yes. Elliptical announcements are common: Dimulai pukul delapan or Mulai pukul delapan. Full sentence style is fine too.

Any quick pronunciation tips for these words?

siaran: see-ah-rahn (3 syllables)
itu: ee-too
dimulai: dee-moo-lai (the ai is like “eye”)
pukul: poo-kool (short, pure vowels)
delapan: də-LA-pan (the first e is a schwa) Indonesian stress is light, usually near the last or second-to-last syllable.

Do I need articles or plural markers? Is siaran countable?

Indonesian has no articles. Siaran can be singular or plural from context. To make it clearly plural you can use banyak/beberapa siaran or reduplication siaran-siaran; to emphasize “one,” use satu/ sebuah siaran (the latter is less common with siaran than with acara).