Translation:I had a party the day before yesterday.
yeah, however, I would like to mention that some Japanese people describe that while seeing 一昨日 in kanji while reading the newspapers they read it as いっさくじつ。As for why is that? is probably because they are used to the formality of newspapers and it just feels more consistent in that case.
おととい like some other users mentioned already is the most used in speech though.
There is also おとつい which is sometimes used by old people and by people in some particular regions.
Two days ago is ふつかまえ（二日前). On the other hand, おととい (一昨日) means the day before yesterday. They both have similar meanings but are different words. Although it can mean more or less the same thing as the day before yesterday, I think that the actual translation into Japanese would be different.
No, while the meaning might be conveyed, it's still weird. You can "throw a party" or "have a party" and those mean mostly the same thing of hosting or organizing the party.
If you "party" you do the action of enjoying the party, not necessarily hosting it. I "did party" is the past perfect tense of that verb "party".
Since the listening questions are automatically generated the answers need to be written exactly as they are taught in the lesson, so おととい is required.
おととい is being taught with hiragana because it's a more common word to use when spoken and the also automatically-generated TTS insists on pronouncing 一昨日 in its very formal less common pronunciation いっさくじつ. The contributors chose to write it in hiragana in order to force the TTS to say the reading they want you to use.
It's an issue that staff really needs to look into since this is a problem with almost all of the time related words in the new course. Considering the contributors had to find these workarounds though it's likely either staff haven't found a good fix yet or it's lower on the priority list. It's best to report these audio problems in an official bug report when you see them. Reporting the audio on the question itself will only notify the contributors who don't have any control over it. All they can do is turn the audio off entirely for the question which also isn't helpful.
Like me, most people are getting confused and get tripped up on the verb stem and particles. In ”。。。をしました”, Shi is the verb for "to do". So said the person "Had a party" and with ”。。。に行きました” Iki is the verb stem for "to go". So, in that sense, it'd be "went to the party". Hope I explained that correctly.
We have a word for "the day before yesterday" in Portuguese (anteontem) but saying "the day before yesterday" sounds sooo weird in English (at least to my non-native-English-speaker brain). I'm glad to know that Japanese has a word equivalent to "anteontem" in Portuguese. I usually go with "two days ago" when speaking English.
Nope, it would become a grammatically incorrect sentence if you excluded it. But if you change "party" to "partied", then it'd make sense without the "a", but the potential implications of the sentence change slightly.
"I had partied" is saying you definitely partied. There's no room for ambiguity.
"I had a party" could mean you hosted a party, but maybe didn't participate. Or perhaps you were invited to one but chose not to go (in either case, you'd clarify that with some extra wording such as "but I didn't go").
That sounds strange in English, like you're making up an excuse for something.
"Why don't you have any of your work done?" "Well...I did party the day before yesterday...a lot" (party being a verb here, not a noun)
It doesn't really have the same nuance of telling someone "I had a party" or "I threw a party", more that you were partying somewhere whether it was you who was throwing the party or not and you've been called out on it. Otherwise we don't "do" a party in English. We just have them or attend them.
can this mean "I gave a party" or only "I went to a party"? The expression "I had a party" in English is ambiguous. I personally would only use it in situations of a planned event "Excuse me, teacher. I couldn't study for the test because I had a party." (!!!) or "I got dressed up because I had a party [to go to]."