Learn Hardcore Indonesian: Saya sudah memeriksa jadwal sebelumnya. - I already checked the schedule beforehand.

Sudah marks that an action is completed (aspect), not past tense. Indonesian doesn’t inflect for tense; time is inferred from context or time words. Here it means the checking is already done relative to the reference time (often “now” unless specified).

Is using both sudah and sebelumnya redundant?

Not redundant. They add different nuances:

Sudah = the action is completed.
Sebelumnya = it happened earlier than some reference point (earlier in the discourse or before another event). Together they can approximate English “had already.”

Where can I put sebelumnya in the sentence?

Common, natural placements:

Clause-initial: Sebelumnya, saya sudah memeriksa jadwal.
Clause-final (as given): Saya sudah memeriksa jadwal sebelumnya.
After the subject (a bit more formal/written): Saya sebelumnya sudah memeriksa jadwal. Avoid splitting the verb and object with it in speech (e.g., Saya sudah memeriksa sebelumnya jadwal)—that sounds odd.

Could jadwal sebelumnya mean “the previous schedule”? How do I avoid that ambiguity?

Yes. Jadwal sebelumnya can mean either “the schedule from earlier” (adverbial) or “the previous version/earlier schedule” (adjectival). To mean “earlier in time,” prefer:

Sebelumnya, saya sudah memeriksa jadwal.
Saya sudah memeriksa jadwal sebelum itu. To mean “the previous schedule,” make it explicit:
Saya sudah memeriksa jadwal yang sebelumnya.
Saya sudah memeriksa jadwal versi sebelumnya.

What’s the difference between sudah and pernah?

Sudah = completed (relevant to the reference time): Saya sudah memeriksa jadwal.
Pernah = ever/at least once at some time (experience): Saya pernah memeriksa jadwal. (Doesn’t imply it’s done for the current situation.)

How do I negate this—use belum or tidak?

Default “not yet”: Saya belum memeriksa jadwal.
Plain negation of doing it (e.g., “I didn’t check earlier”): Saya tidak memeriksa jadwal sebelumnya. Use belum when there’s an expectation it may still happen.

Is there a more formal or more casual alternative to sudah?

More formal: telah — Saya telah memeriksa jadwal sebelumnya.
More casual: udah (spoken) — Saya udah meriksa jadwal sebelumnya.

Is memeriksa the best verb for “check” here? What about casual options?

Memeriksa is correct and fairly neutral/formal. Common casual/neutral alternatives:

mengecek: Saya sudah mengecek jadwal.
cek (very informal): Saya udah cek jadwal. Colloquially, memeriksa may be pronounced/written meriksa. Note memeriksa also means “to examine/inspect” (e.g., Dokter memeriksa pasien).

What’s the nuance of Saya vs aku vs gue/gua vs addressing Anda?

Saya: neutral/polite standard.
Aku: informal/intimate.
Gue/Gua: very informal, Jakarta slang.
Formal “you” is Anda. Examples: Aku sudah mengecek jadwal sebelumnya. / Gue udah cek jadwal sebelumnya. / Apakah Anda sudah memeriksa jadwal?

Do I need -nya on jadwal?

Not required. Jadwal can be definite from context. Use -nya to mark a specific/known schedule (or “his/her” schedule):

Saya sudah memeriksa jadwalnya. Very formal “that schedule”: jadwal tersebut.

Can I drop the subject Saya?

Yes, in context Indonesian often drops pronouns:

Sudah memeriksa jadwal sebelumnya. Make sure context makes the subject clear.

How do I ask “Have you checked the schedule (yet/earlier)” naturally?

Formal: Apakah Anda sudah memeriksa jadwal (sebelumnya)?
Neutral: Anda sudah cek jadwalnya?
Very common casual pattern: Udah cek jadwalnya belum?

How do I say “I had already checked the schedule (before he arrived)”?

Use sudah plus a time clause:

Waktu dia datang, saya sudah memeriksa jadwal.
Sebelum dia datang, saya sudah memeriksa jadwal. Adding sebelumnya can reinforce the prior timing, but the time clause is what disambiguates.