In astrology, there is the concept of "birth time rectification (BTR)".
As that website says (the site seems to be copy-protected), in natal astrology, knowing the time of birth (TOB) is vital for the predictions to be correct. But most natives are unsure of the exact TOBs for whatever reasons.
So, the astrologer corrects the TOB by using some methods. What I find strange here is that in the calculations, the astrologer uses the TOB that the native provides him with (which is inaccurate).
So my questions are how the astrologer does the BTR using the TOB of the native, which according the astrologer, is inaccurate? What methods are used here?
How can the astrologer come up with the correct TOB by using a chart which is cast using an incorrect/approximate TOB?