"I had a party the day before yesterday."
I think it says something like "issakujitsu" can anyone confirm what its literal translation is?
Reading of 一昨日 can be one of:（おととい、おとつい、いっさくじつ）. Same meaning. いっさくじつ sounds more formal.
Mate, this is something that has no reason. It is a language feature. In English there are a few examples: syrup (seer-up vs sirr-up), almond (al-mond vs am-end vs ahl-mend), adult (add-ult vs uh-dult)
That's interesting. I thought there might be origins of the different ways or something.
Okay you want the history on how these pronunciations were originated.
The origin was 「をとつひ」. をと（遠 or 彼方） meant "far away", つ was the old form of の, and ひ（日）is day. So it meant "A day which is far away."
This became おとつい and eventually おととい in pronunciation.
Kanji 一昨日 was introduced when Chinese characters started to be used in Japan. Since then, the Chinese reading (On'yomi) was introduced as いっさくじつ.
both means pass tense polite form. Former is used with verbs and latter one with nouns
Desu is a copula or "to be." Basically, you are not being a party, nor are you saying something is a party. That is a simple way of viewing it.
How come in this sentence the connective between "the day before yesterday" and "party" is "は", however in this sentence: "金よう日にパーティーをします" (I will have a party on Friday) the connective between "Friday" and "Party" is "に"? Thanks
We do not use に for おととい. に is optional for days of week like 金曜日. は is the topic/contrast indicator and is optional too.
Is particle order reversible in context? This was not acceptable but should it be? パーチイーをおとといはしました。
Dates, days of the week, month, year, time, are by default at the front of the sentence, exceptions would be names, i, you, me, him, her, salutations, addressing people etc.
おとといはパーテイーをしました You used the wrong word. おとといはパーティーをしました
Could anyone let me know please how I get that small イ using Microsoft IME?
いました does not mean "I had." It means "There existed (animated objects)."
I had a party cannot be directly translated in Japanese. It is either "I did a party" or "I participated in a party." In Japanese they are パーティーをしました or パーティーに参加（さんか）しました.
I'm just really confused because on the comment section for the question before this it said that there isn't a linking word between time and the object? But this time there is?
は is not a linking word. It is the emphasis particle which says that the word before is a topic or emphasis of the sentence. You can include は or omit は depending on whether you need the emphasis.
Can anybody explain the kanji for おととい （一昨日) I know its the kanji for "one", then something and then the kanji for day.
the kanji 昨 means yesterday/previous. the actual word "yesterday" is 昨日 (きのう). so then 一昨日 is like "one day before yesterday"
the lesson said that the を was optional in cases like this, but omitting it here was not accepted.