Whats the earliest time (not date, but hour in the evening) can one say kiddush lavanah? Is it tzeis hacochovim? Or after shkiah? Are there different opinions?
The Rema (426:1) writes that Kiddush Levanah should not be said before nightfall, meaning tzeis hakochavim. The Mishnah Berurah writes that it should not be said in bein ha-shmashos.
The Shulchan Aruch himself does not mention this point, and it is possible that according to the Shulchan Aruch Kiddush Levanah can be said even before nightfall.
However, the halachah follows the Rema (as later poskim assume), and this is certainly true where the Shulchan Aruch makes no mentions of the issue, so that it is possible he agrees with the ruling (though he also doesn’t mention it in the Beis Yosef).