There are different calculations based on interpretations of different Puranas as to the period of yugas. Different scholars interpret it differently. None of these scholars is a Yogi who knows about the future. Besides the Puranas are quite symbolic in their content and not regarded as a completely authoritative scripture as we regard the Vedas, Upanishads, and the Gita.
However, just plain common sense would tell us how flawed some of these scholars could be. For example there is at least some historical evidence of the two major Avatars during which the Yuga changed. Lord Rama’s bridge (Ramasetu), still visible by Satellite images is roughly 18000 years (about 16000 BC) old. Similarly the Mahabharata War is about 6000 years ago (about 4000 BC). This means there is roughly 12000 years gap between the closing of Treta and the closing of Dwapara. This corresponds to one of the interpretations of dates which explain that the number of years from one Age to another reduces by half each time. That is to say the Avatars come in lesser gaps of Time which makes perfect sense given that the degeneration of Dharma is more and more rapid with change over from one Age to another. If that be so then the gap between Sri Krishna and the next Avatar should be roughly 6000 years which is where we stand today. I have given a talk on this subject and so have quite a few others with similar or different hypothesis. In any case, Sri Aurobindo and the Mother were both trikaladarshis. Their prophecies about significant world events such as India’s independence, defeat of Hitler in the second world war, India’s victory in the Bangladesh War, the splitting of Pakistan into five parts, rise of Asia and India, india’s spiritual gift to the world, rise of Sanatan Dharma are all come true or on the way of coming true. So we can safely say that there word about the beginning of the first steps of Satyuga after 29th February 1956 is true.
Affectionately,
Alok Da