I am answering this question acording to the Garuda Purana
Jiva loses the memory of its previous births at the moment he comes out of the mother's womb.
It has been mentioned multiple times in the Garuda Purana.
The following is the statement made by the lord Vishnu in conversation with Garuda stating that the human forgets the knowledge of previous births ...
Thanks to the eternal Srimad Bhagwad Gita which elaborates facts pretty simply(knowing such facts isn't any way possible as such in a lifetime):
As per the 'time of death' one can know what's the basic outcomes of the being:
यत्र काले त्वनावृत्तिमावृत्तिं चैव योगिन: |
प्रयाता यान्ति तं कालं वक्ष्यामि भरतर्षभ || 23||
अग्निर्ज्योतिरह: शुक्ल: षण्मासा उत्तरायणम् ...