In discussing the creation of the world the Talmud describes the different opinions as to the time of creation.
R. Yehoshua holds that the world was created in the Nissan season; man was created on the first of Nissan and the first stages of creation - Bereishis - began on the 25th of Adar.
According to this opinion, the 25th of Adar, is the birthday of the world.
Rabbi Eliezer was of the opinion that the world was created in Elul-Tishrei.
Chassidus explains the rapprochement of the two opinions in the following way.
The supernal thought to create the world blossomed in the Nissan season, while the reality came in Tishrei.
The "creation" of Nissan therefore possesses the quality of thought over action.
Years later, when the Tabernacle was first erected on the first day of Nissan it also brought greater stability to the world for the thought was combine d with the action (see Bereishis Rabbah 12:11).