Hi, Almost exactly two years ago my wife and I “took on” the zman of Rabbeinu Tam for tzais shabbos. As far as I remember there was no formal declaration. Rather, something we just started doing (on the other hand there were times that we said to people who spent shabbos by us something like “just so you know, we keep zman r”t for tzais shabbos.” Don’t know if that counts as a “declaration”).
As we’ve been doing this for these last two years, I have noticed quite a few people who we hold to be tremendous baalei aliyah and talmidei chachomim – people who seem to hold other tremendous chumros in their own life – who do not keep zman r”t for tzais shabbos. I am starting to wonder – is this a chumro, is it something else, is it something not necessary? The reason we did it was to make a greater effort in not “rushing” shabbos out. Of course, I could just daven at a nice slow maariv on motz”s or even wait to catch the second or third one. But this seemed to just make more sense. I am now realizing that I don’t fully grasp it and am wondering if we’re doing something unnecessary. Thank you.
What you are doing is a good thing, and you should keep it up! The topic of Bein Hashmashosh is very big, and one of the main opinions is known as the opinion of Rabeinu Tam, which is really Rabeinu Tam and another 20 rishonim, who hold that it is night time 4 parso walking distance after the sun sets, and that is when it is really dark and the stars come out. One of the main controversies with this is that in many countries we see that it gets dark and there are three stars way before 72 minutes. ( Minchas Cohen) This is one of the reasons that in Eretz Yisroel most poskim say to keep shabbos until 25-40 minutes after sunset, it is because they hold that this is like the opinion of Rabeinu Tam for Eretz Yisroel. There are others however that say that for the honor of Shabbos, and because it is a mitzvah D’oraysa, that it is commendable to wait and not do Melacha until 72 minutes after shkia.
As a side point I personally know tzaddikim that would wait 72 minutes on motzei shabbos for this very reason.
See Lehros Nosan 2-14, Minchas Yitzchok 4-53.