Next Tuesday night should be the first night of Pesach according to the approach of the gemara in Sanhedrin page 10 side b.--that is you go by the conjunction of the moon with the sun on the same longitude.[not the same latitude also because that would be lunar ellipse]. And that is the first opinion of Tosphot over there. But if you go by the gemara in Rosh Hashana, there it is clear you go by the time when you can see the new moon, and that would be a day later. [That is the gemara that Tosphot bringc to argue on that first opinion. [ But in my opinion, that Gemara in Sanhedrin disagrees with the Gemara in Rosh Hashana] But none of that has anything to do with the calendar. All this means is if there would be a court that had authentic semicha from Sinai then they would go by one of these opinions the conjunction or when they see the new moon
