The 14th day of every lunar month or the day before the new moon is known as Shivarathri. Among all the 12 Shivarathris that occur in a calendar year, Mahashivarathri, the one that occurs in February-March, is of the most spiritual significance.
On this night, the northern hemisphere of the planet is positioned in such a way that there is a natural upsurge of energy in a human being. This is a day when nature is pushing one towards one's spiritual peak. It is to make use of this, that in this tradition, we establish a certain festival which is night-long. One of the fundamentals of this festival is to ensure that you remain with your spine vertical and awake.
Mahashivarathri is very significant for people who are on the spiritual path.
For the ascetics, it is the day he became one with the Kailash – absolutely still. In the yogic tradition, Shiva is not worshipped as a God, but considered as the Adi Guru, the first Guru from whom the knowledge originated. Modern science has gone through many phases and has now arrived at a point where it is out to prove that everything that you know as life, as matter and existence, as the cosmos and galaxies, is just an energy that manifests itself in millions of ways.
This scientific fact is an experiential reality in every yogi. The word "yogi" means one who has realised the oneness of existence. When I say "yoga," I am not referring to any one particular practice. All longing to know the unbounded, all longing to know the oneness in the existence is yoga. The night of Mahashivarathri offers a person an opportunity to experience this.