“O great saintly person, you have compiled the astrological knowledge by which one can understand past and present unseen things. By the strength of this knowledge, any human being can understand what he has done in his past life and how it affects his present life. This is known to you.” [Śrīmad-Bhāgavatam 10.8.5]
From the Purport: Although this body is temporary, as long as we have to live in this body we must suffer. Whether one has a short life or a long life, one must suffer the threefold miseries of material life. Therefore any gentleman, dhīra, must be interested in jyotiṣa, astrology. Nanda Mahārāja was trying to take advantage of the opportunity afforded by Garga Muni’s presence, for Garga Muni was a great authority in this knowledge of astrology, by which one can see the unseen events of past, present and future. It is the duty of a father to understand the astrological position of his children and do what is needed for their happiness.