"I know when the party is."
Translation:Yo sé cuándo es la fiesta.
It's not about it being necessary or not. It's about whether it has to be accented or it has to be unaccented. The accented
cuándo is used for questions. Otherwise, non-accented
cuando is used.
¿Cuándo empiezas a trabajar? (When do you start working?)
Voy a empezar a trabajar cuando termine de estudiar. (I will start working when I finish studying.)
Yeah, the real rule is that unaccented cuando is used for adverbial clauses.
For example: Yo sé cuándo son las seis en la mañana cuando el gallo cacarea. I know when it is six in the morning when the rooster crows.
The cuándo is saying what I know, that it is six in the morning. The unaccented cuando starts a clause that describes how or, of course, when the action takes place; upon the rooster crowing.
I understand that we are learning Spanish and that you were clarifying the placement of an accent, for which, I thank you, but I believe you have one too many 'whens' in your sentence. Either "I know it is six in the morning when the rooster crows." or "I know when it is six in the morning the rooster crows." or am I mistaken?
Ah so redundancy in "a mi padre le interesan los deportes" is totally fine.
And the personal a that is used for both direct and indirect object is ok too ex: deja a José solo (leave José alone), deja unos chocolates a José (leave some chocolate to José)
But "I know it, when the party starts" is unacceptably wrong, although it is totally the oposit and can be said in a situation like this below:
A told B yesterday: I wish I know when the party starts. B comes the next day and tells A with enthousisam: I know it, (then continues to explain himself) when the party starts.
Unfortunately, that rule is an oversimplification. The use here is close to asking a question; it's saying that I know the answer to the question. It's not introducing an adverbial clause.
Compare ‘Yo lo sé cuando la fiesta es.’; that's a little weird and required a couple of other adjustments to be grammatically correct, but it means that the time when I don't know some thing is at the same time as the party.
Conocer is used for knowing a person or place. Saber is used for knowledge of facts, etc. Have a look at this page for more info: https://www.spanishdict.com/guide/saber-vs-conocer