While we are already have passed Rabbeinu's birthday of the 1st of Nissan, there's the well known hint to Rabbeinu where in the words - V'Im Ayin Mechani Na M'Sifrecha- "If not, please erase me from Your book" (Exodus 32:32) in which when the letters are spelled backwards, it reads Ani Nachman - "I am Nachman", and the Roshei Teivos of these words is Me'Uman. To think of it, the word Ani "I" also hints to Rabbeinu's birthday of the 1st of Nissan, as the letters of this word is the first part of the date of Alef Nissan - as the letters are Alef, Noon, Yud, being that the first two letters of the month of Nissan are Noon & Yud.
This quoted verse is in the context of Moshe Rabbeinu pleading to Hashem to forgive Klal Yisroel for the sin of the Eigel HaZahav. This Aveira for all practical purposes was a negation on behalf of the ones who worshipped it of the Korban Pesach that they brought in Mitzrayim to show the Mitzrayim that their god was being used as a Korban to be slaughtered and eaten. Another reason for this was to negate the powers of the constellation of the month of Nissan - Taleh/lamb, which the Egyptians worshipped, and hence, to turn their Mazel around in favor of the Jewish people, who are in fact above nature. And more directly related to the 1st of Nissan, it was on this very date - Rabbeinu's birthday - that Hashem told Moshe Rabbeinu to tell Klal Yisroel the Mitzva of the Korban Pesach. And as we know, the word Pesach is the same Gematria as Rabbeinu's name Nachman - 148.