Learn Hardcore Indonesian: Kami mengirim perubahan jadwal lewat pesan singkat. - We send the schedule change via a short message.

Kami = we (excluding the listener).
Kita = we (including the listener). If you’re telling the listener that they are also part of the group, use kita; otherwise use kami.

Does mengirim mark past, present, or future? How do I say each?

Indonesian verbs don’t mark tense. Add time/aspect words:

Can I say kirim instead of mengirim?

Yes, in everyday/colloquial speech: Kami kirim perubahan jadwal... In more formal writing, prefer mengirim (or mengirimkan).

When do I use mengirim, mengirimkan, and mengirimi?

mengirim: neutral, object is the thing sent. Example: Kami mengirim perubahan jadwal.
mengirimkan: often interchangeable with mengirim, slightly more formal/polite or emphasizing the item/act. Example: Kami mengirimkan perubahan jadwal kepada Anda.
mengirimi: takes the recipient as the direct object. Example: Kami mengirimi Anda perubahan jadwal.

Is perubahan jadwal singular or plural? How do I say “a change” or “some changes”?

It’s neutral (could be one or many). To be explicit:

Is mengirim perubahan jadwal natural, or should it be mengirim pemberitahuan perubahan jadwal?

Both are fine:

mengirim perubahan jadwal: you sent the revised schedule or the changes themselves.
mengirim pemberitahuan perubahan jadwal: you sent a notification about the change(s). This is common in formal notices.

What does lewat mean here? Can I use melalui or via?

lewat means “through/by means of.” Alternatives:

melalui: more formal. Example: ... melalui pesan singkat.
via: borrowed, common in writing. Example: ... via pesan singkat. Casual options: pakai (very informal), dengan (OK but less specific about the channel).

What exactly is pesan singkat? Is it SMS or any text message?

Literally “short message.” It often refers to SMS, but can be understood as a generic text. To be specific, say:

Can I move lewat pesan singkat to another position?

Yes:

Neutral: Kami mengirim perubahan jadwal lewat pesan singkat.
Fronted channel: Lewat pesan singkat, kami mengirim perubahan jadwal.
Object fronting (colloquial): Perubahan jadwal kami kirim lewat pesan singkat. Avoid: Kami mengirim lewat pesan singkat perubahan jadwal (sounds awkward).

How do I say it in the passive voice?

How do I add the recipient (e.g., “to you/the team”)?

Use kepada for people/groups:

Kami mengirim perubahan jadwal kepada Anda/kepada tim. Untuk focuses on “for the benefit of”: Kami mengirim perubahan jadwal untuk Anda.

How do I make the sentence more polite/formal?

Kami telah mengirimkan pemberitahuan perubahan jadwal melalui pesan singkat kepada Bapak/Ibu. Tips: use telah, mengirimkan, melalui, and address the recipient as Bapak/Ibu or Anda in formal contexts.

Why is there no article like “the”? How do I say “the schedule change”?

Indonesian has no articles. Use demonstratives or possessives:

perubahan jadwal itu/tersebut = the schedule change(s)
perubahan jadwal kami = our schedule change(s) Note: perubahan jadwalnya means changes to his/her/its schedule.

What’s the difference between jadwal, agenda, and rencana?

jadwal: a timetable/schedule with times (what happens when).
agenda: list of items/topics (e.g., meeting agenda).
rencana: plan (intentions/arrangements, not necessarily time-bound). So perubahan jadwal is specifically a change to the timetable.

What’s the word formation of perubahan?

Root ubah (to change) + nominalizing pe-...-an → perubahan (a change/changes). Related forms: