By referring various articles in spirituality and prosperity, my thoughts on “many birth day in a year” is as follows:

The birthday what we celebrate is of the birth of the body. But the birthday Sri Karmayogi speaks is of birth of the soul at higher level than this embodiment will permit. In our tradition the soul is not born except when it leaves the body to be reborn elsewhere. But for one who initiates to invoke spirit the initiation is considered the second birth, the first being the physical birth.

“Initiation as well as realization are supposed to give a further lease of life equal to what he has so far lived. In a conscious person, conscious of his soul, on the birthday the Soul seeks a rebirth, a birth into higher consciousness. Celebration of his birthday is the celebration of this higher birth. It is not necessarily once in twelve months. It may be earlier depending upon his own awakening in the Soul. For those who do integral yoga, it is a yogic possibility that they can be reborn every day. Others find such men wiser than their years.

For example, One Muni who saw Sri Aurobindo called Him Puradhana Purusha of 500 years old and explained that in Him he found the wisdom of 500 years. Maybe He was reborn in His Soul 500 times in this birth”.

Sri Karmayogi says, If our consciousness is plastic and fresh, everyday will be a learning experience akin to taking a new birth. The goal of purna yoga is to be as fresh as possible like a new blossom opening every day. Unfortunately, people are so ossified and routine in their thoughts and habits and way of functioning that the goal of ever-present freshness remains a distant dream for a majority of devotees. On the birthday a devotee’s soul is somewhat active and so Sri Karmayogi  says it is an occasion for the person to grow.