Sulla, I've considered those questions before have decided , FOR MYSELF, that the precise date/time/etc... is not important.
I accept that all Christians have their belief system part right and part wrong. I'm no exception. If the absolute correct way to understand things was so vital that our eternal salvation hinged on it, then I believe it would be a lot more obvious to everyone. That approach applies to every doctrine I hold to be true, according to my fluid understanding of things, and to the method by which I commemorate Christ's sacrifice.
In my opinion, none of us are going to be found acceptable by God because we had all our T's crossed and I's dotted. Ain't NObody gonna walk in to paradise because they got all the multiple choice questions right. The main reason I take this attitude toward it is: I'm not a bible scholar and never will be. Beyond my willingness to be led by holy spirit, I would be at the mercy of other people's (even scholarly) opinions. Right or wrong, I am confident I am doing things correct enough, or I would be adjusted by "the teacher".
Like my understanding of the scriptures in general, I will follow Christ's instructions regarding this event to the best of my personal understanding. I prefer not to promote any aspect of it so that I don't come between someone else and their right to arrive at an acceptable arrangement between themselves and their conscience.
I understand your questions, though. I was asking the same things before I partook at home last year - I was curious about the format used by others. Ironically, I never got a straight answer from anyone. Nothing in depth, anyways. I'm kinda glad it worked out that way. Now, the program of worship I have with God is MINE. Come judgement day, God will look at me and say, "Jason, I see what YOU did here."