"I will come the day after tomorrow."
Translation:Saya akan datang lusa.
But I thought "akan" wasn't supposed to be used when there is another indication in the sentence of the time of occurence of the verb. Doesn't "lusa" make "akan" redundant, or does it serve for emphasis here or something? Like is this the way you answer the question "Kamu datang lusa?" but not the way you state it if it's new information?
It's okay to use "akan" even when there is another indication of (future) time.
Absolutely nothing wrong with that.
It's the preferred way to use it in the formal setting.
For me personally, I always use it in a formal setting.
However, in everyday/colloquial speech, in a sentence like this, "akan" can be omitted.