Learn Hardcore Indonesian: Rapat diadakan di kantor besok pagi. - The meeting is held at the office tomorrow morning.

In Indonesian, passive voice is formed by adding the prefix di- to the verb root. The root of mengadakan (to hold/organize) is adakan. So:

mengadakan = active form (“to hold”)
diadakan = passive form (“is/was/will be held”)

In Rapat diadakan di kantor besok pagi, the focus is on the meeting itself rather than who organizes it, so we use the passive diadakan.

What is the function of the two dis in diadakan and in di kantor? Are they the same?

They look identical but serve different roles:

The di- in diadakan is a verb prefix marking passive voice.
The di in di kantor is a preposition meaning “in/at.”

Context tells you whether di is part of the verb or a separate preposition.

Why doesn’t the sentence tell us who holds the meeting? How would you include the organizer?

In passive constructions, Indonesian often omits the agent when it’s obvious or not important to mention. To explicitly include the organizer, use oleh + agent: Rapat diadakan oleh manajemen
= “The meeting is held by management.”
Here oleh manajemen clearly marks who does the action.

Where do time and place phrases like besok pagi and di kantor go in Indonesian sentences? Can their order change?

Time and place phrases are quite flexible. A common pattern is: Subject + Verb + Place + Time
But you can rearrange for emphasis:

Besok pagi, rapat diadakan di kantor.
Rapat diadakan besok pagi di kantor.
Di kantor besok pagi, rapat diadakan.

All versions are acceptable; native speakers will understand the schedule and location regardless of the order.

Why is there no article before rapat? How do you say “a meeting” or “the meeting” in Indonesian?

Indonesian does not use articles like “a” or “the.” You can add specificity with words such as:

sebuah rapat = “a meeting” (indefinite)
rapat itu or rapat ini = “that meeting” / “this meeting” (definite)

Without those modifiers, rapat is understood from context.

How would you express the same idea in active voice: “The office holds a meeting tomorrow morning”?

Switch to active voice by making the organizer the subject and using meng-: Kantor mengadakan rapat besok pagi.
Literally: “Office holds meeting tomorrow morning.”
You can add more detail if needed, e.g. Kantor pusat mengadakan rapat besok pagi.

Do you need to add akan to indicate future tense, like Rapat akan diadakan di kantor besok pagi?

Indonesian verbs aren’t inflected for tense; time adverbs like besok pagi already show the future.

Without akan: Rapat diadakan di kantor besok pagi (scheduled for tomorrow)
With akan: Rapat akan diadakan di kantor besok pagi (adds emphasis on future)
Both are correct. Akan is optional when you already have a clear time expression.