Yep, "I had reached the moment" appears correct at first, but to explain why it isn't:
"Llegar" is an intransitive verb, meaning it naturally refers to the subject and does not take a direct object. So, in the absence of a preposition, "el momento" is the subject regardless of whether it precedes or follows the verb: "Había llegado (el momento)"="It had arrived (the moment)">"The moment had arrived."
To give the subject a destination we need to follow "llegar" with a preposition of movement, such as "a." This tells us the subject had arrived "to" a destination: "Había llegado al momento"="I (it/he/she) had arrived [to] the moment">"I had reached the moment."
I can't guarantee this is how native speakers express this exact sentiment, but structurally it is correct. Hope that clarifies.
My first try was "he has arrived the moment", and so I thought "the moment has arrived?" --> i wonder if that would have been a suitable translation. I wish we could choose whether to repeat the same sentences in different formats (this came up as a speaking exercise for me; I'd have loved to have a go at translating it myself to see if my translation would be accepted)
I think that "El momento" cannot be an object in this Spanish sentence, because "llegar" is an intransitive verb, and there is no prepositional phrase (e.g. "a el/la ___"). So, the only option is for "el momento" to be the subject.
However, I would think that "Había llegado al momento" is a grammatical sentence for expressing "I/he/she/you(Usted) had arrived at the moment"--though I'm not sure if it sounds alright to a Spanish speaker. (The English is OK, though is improved if "the moment" is given more context e.g. "the moment of truth.")
Type in "I had reached the moment" into SpanishDict.com and you get "Habia llegado el momento". Then type in "Habia llegado el momento" and you get both "the time had come" and "the moment had come". But when you think about it logically "I had reached the moment" is a rather useless sentence.
Duo usually requires us to be so spot on with translation that it is hard to think away from very literal translations.
Hey, DL. Any chance you could kind of ease us into a completely new subject, rather than throwing something like this at us right off the bat? It would be dead easy to introduce this phrase as a spoken exercise with a translation given, so we'd become aware of the possibility of this sentence construction before being asked to create it ourselves.
My theory is that it often elicits a period of time when language is learned. I recall learning to think in English prior to speaking English as a native language. Full sentences. I don't think I said them out loud then at all tho. So the brain begins to hear and keep and then use the words, and then ....there is always more.
I'm not sure I would call it shack, but I agree that these surprises can be a positive. Sometimes I can catch them and that feels good. Other times, they catch me. Then I get curious and start looking around to find examples or insights.
I believe it's helping that I've been listening to a lot of Spanish pop music. Song lyrics do word play and rely on turns of phrases. I admit I'm also worried about trying those phrases out on Spanish-speaking colleagues at work...
"Había llegado al momento." and "Había llegado el momento." every one has one different meaning.
"Había llegado al momento." Also can mean that he or she had come soon after of thing.
"Había llegado el momento" means the moment waited for example a birth, a test, a marriage,