This year is a leap year according to the Jewish calendar. Why do we need leap years? We need leap years because Pesach (passover) is not allowed to be celebrated at any other time of the year except in the spring. And if we did not have a leap year with the extra month of Adar added in then Pesach would not be celebrated in the spring and would continually get earlier and earlier according to the Solar calendar.
Rav Zev Leff in his book Festivals of Life- talks about the significance of two Adars and their meanings. I am going to summarize what I read and put it in my own words but the ideas are his.
The two Adars are representatives of the spiritual and physical worlds. The first Adar is a completely spiritual one that is likened to Olam Habah ( the next world). It is also likened to the moon the hidden one. In Adar alef while we are aware that Purim and all the miracles are coming, we aren’t immersed in the physical aspects of them. Which allows us to focus on the tremendous spiritual feeling that is in the air. Adar Bet where we celebrate the holiday of Purim which is bringing to life the saving of the Jews in the Persian Empire, and recognizing G-d even though he is hidden, reminding us that G-d is always with us. It is about elevating the physical to the spiritual. What is drinking really about on Purim, its not about getting drunk and being silly. It is also not just about not being able to tell the difference between Mordechai and Haman. Its about allowing our souls to shine through, to remind us of who we really are on the inside in order to remind us that we are special people, and not just a chunk of meat. That we have a purpose in this world and we have an obligation to strengthen G-ds presence in this world by doing things that bring his light into this world. It is two fold not only are we elevating the physical to the spiritual, but we are combing the two by bringing G-d into this world in a more concrete form. Purim is a holiday of intense Joy but that joy should not be physical it should be a spiritual connection to our creator, in that we find him in every aspect of our lives.