If the world was created in Nisan (beginning with 25 Adar) like R’ Eliezer and the machshava to create the world was 40 days before, then Hashem decided to create the world on 15 Shevat! Why does Beit Shammai hold like R’ Eliezer and Beit Hillel like R’ Yehoshua?
If we are destined to be redeemed in Nisan then 40 days before – Tu B’Shevat – is the beginning of the redemption process. The Gemara, based on Yechezkel 36:8, says that a suresign of the redemption is the Land of Israel giving forth its fruit. This is the meaning of being judged for פירות האילן on Tu B’Shvat.
Shiur provided courtesy of Torah Anytime