Actually with 5 crystals you will be forced to ascend with companions or ascend alone. So 1-4 crystals: you and areelu, 5: you and party, 6: all ;)

Is the year important or just the day and month? If we miss the window in 4717, can we make it in 4718?

As a few others have mentioned, some of the information in the lists for these endings aren't necessary or are just confusingly worded. Here are the changes I've discovered or the things I've missed due to poor wording and still succeeded at the ASCENSION ENDING:

Act 5
• "Explore the woods next to the house, find a winder, use the key." = I never found a "winder" and so never "used the key."
• "Find Areelu's notes at the shelf. Research them." = Somehow I ended up with two event cards to research these notes; I'm not sure if there was a second place that I obtained them or if this was a bug

Continue Act 5
• "Exit the passage, go right, pass an athletic check, talk to the NPCs there, use all dialogues." = After defeating the purple wurm, there's a passage that takes you outside of the prison and back to the area entrance; this didn't require an Athletics check and there were no NPCs there so I figured this wasn't what that sentence was referring to. However, when exiting the same way you entered these caverns, there was no pathway to the right. I ended up never talking to these NPCs unless this is somewhere else in the prison. This could use some clarification.
• "Enter the Threshold between the 16th and 21st of Gozran 4717." = I ended up skipping past this date doing event cards; I skipped days for an entire year to get back to this date in 4718 and was able to ascend. The year is inconsequential; only the days in that month matter.
• "Enter the shrine near the entrance of the next building, and activate it." = I have no idea where this "shrine" is located. I searched all over every one of the three or four maps you go through when doing Thronehold and never found any other building entrances and was still able to ascend.
• "Speak to Areelu after defeating the Echo of Discari, ask her all the questions before fighting her." = This may have just been my lack of attention to detail, but for some reason I thought I wasn't supposed to fight her and kept reloading thinking that I had chosen the wrong dialogues or screwed up the ascension path somewhere along the way. You have to fight her first and then you're able to convince her not to continue with the process.

Just a headsup, even if you fulfilled all the prerequisites, you can still lock yourself out of this ending if after fighting Areelu at Threshold, you comment that you "understand the nature of her preparations" (may require the skill check before the fight). That dialogue option leads to 3 options:
-a diplomacy check (if passed she'll give up)
-an intimidation check (if passed she'll give up)
-option without a skill check (starts another fight)

I forget what i answer yaniel with on Act3 Drezen
did this lock me out of this ending if i answer wrong one

Where is the Shrine in Threshold?

where in the conversation with Areelu in Act 4 is the perception check for "being surprised by Suture"?

Not gonna lie, this was 100% not worth the effort of going through the Enigma

Just made some major edits to this guide, bringing it up to date with the latest changes and fixing some glaring mistakes and omissions. Hopefully it doesn't suck as much now.

Thanks for this update guide! <3